Symposium Organizers
Andreas Lendlein, Helmholtz-Zentrum Geesthacht
Kevin Cavicchi, University of Akron
LaShanda Korley, Case Western Reserve University
Bernd Rehm, Massey University
Symposium Support
MedShape, Inc.
MilliporeSigma
SM8.1: Stimuli-Sensitive Polymers I
Session Chairs
Tuesday PM, April 18, 2017
PCC North, 100 Level, Room 124 A
11:30 AM - SM8.1.01
Rubber-Like Hydrogel Adhesives
Malav Desai 1 3 2 , Eddie Wang 1 , Ju Hun Lee 1 3 , Seung-Wuk Lee 1 2 3
1 Bioengineering, University of California, Berkeley, Berkeley, California, United States, 3 Biological Systems and Engineering, Lawrence Berkeley National Laboratory, Berkeley, California, United States, 2 Bioengineering, University of California, San Francisco, San Francisco, California, United States
Show AbstractCommonly used tissue adhesives are in the form of polymerizing glues or hydrogels. However, cyanoacrylate-based materials from stiff adhesions and polyethylene glycol or protein based hydrogel adhesives have poor extensibility, both of which can potentially cause damage to the treatment site. In this work, we create a robust, highly deformable hydrogel that can be used as a soft tissue adhesive that employs mussel-inspired chemistry. Instead of focusing on developing complex strategies that involve composites and double networks, we use elastin-like polypeptides (ELPs) to create highly flexible and resilient single-network hydrogels. ELPs are recombinantly expressed proteins composed of a tandemly repeated pentapeptide, ‘Val-Pro-Gly-Xaa-Gly’, derived from mammalian elastin. The guest residue ‘Xaa’ can be anything other than a proline. ELP is ideal for developing a highly extensible hydrogel due to its characteristic behavior like an entropic spring that recoils to lower its entropy when stretched. We designed our ELPs to contain reactive amine containing ‘Lys or thiol containing ‘Cys’ residues only at the ends of the polymer chain. This allows us to crosslink the ELP chains into a near-ideal network and utilize the entire length of the polymer during hydrogel extension. We further designed the ELP chains to contain ‘Glu’ guest residues, adding carboxylic acid functional groups. The carboxylic acids are modified with dopamine to enable the hydrogels to undergo mussel-like adhesion on wet surfaces. In this manner, we create protein-based rubber-like resilient hydrogels and characterize their mechanical properties and adhesiveness to wet surfaces such as tissues.
11:45 AM - *SM8.1.02
Evolution of Self-Oscillating Polymer Gels as Advanced Materials
Ryo Yoshida 1
1 , University of Tokyo, Tokyo Japan
Show AbstractIn living systems, there are many autonomous and oscillatory phenomena to sustain life such as heart palpitations and breathing. We developed “self-oscillating” polymer gels that undergo spontaneous cyclic swelling–deswelling changes without any on–off switching of external stimuli, as with heart muscle. The self-oscillating gels were designed by utilizing the Belousov-Zhabotinsky (BZ) reaction, an oscillating reaction, as a chemical model of the TCA cycle. We have systematically studied these self-oscillating polymer gels since they were first reported in 1996 (JACS). Potential applications of the self-oscillating polymers and gels include several kinds of functional material systems, such as biomimetic actuators, mass transport systems and functional fluids. For example, it was demonstrated that an object was autonomously transported in the tubular self-oscillating gel by the peristaltic pumping motion similar to an intestine. Further, self-oscillating polymer brush surface was prepared by SI-ATRP and the dynamic behavior was evaluated. Besides, autonomous viscosity oscillation was realized utilizing microgels, metallo-supramolecular complex, block copolymer solution, etc. Self-oscillation between unimer/micelle or unimer/vesicle (polymersome) structures was also realized for a synthetic block copolymer. At the microscopic level, oscillatory shape deformations of cells are often observed in dynamic behaviors during cell migration, morphogenesis, etc. In many cases, oscillatory behaviors of cells are not simplistic but complex with diverse deformations. We report a more cell-like hollow sphere composed of self-oscillating microgels, that is, a colloidosome that exhibits drastic shape oscillation in addition to swelling/deswelling oscillations driven by an oscillatory reaction. The resulting oscillatory profile waveform becomes markedly more complex than a conventional one. Especially for larger colloidosomes, multiple buckling and moving buckling points are observed to be analogous to cells. In this presentation, our recent progress on the self-oscillating polymer gels is summarized.
12:15 PM - SM8.1.03
Ultra-Stable and Refrigeration-Free Antibody Ionic Liquids
Joseph Slocik 1 , Patrick Dennis 1 , Rajesh Naik 1
1 , Air Force Research Laboratory, Dayton, Ohio, United States
Show AbstractAntibodies represent the gold standard for diagnostic assays (Enzyme linked immunosorbent assay - ELISA), therapeutics (anti-venoms), and the development of antibody based biosensors; however, they require stringent storage and handling conditions in order to retain function. Conversely, the presence of water is very detrimental to antibodies by increasing the rate of hydrolysis and oxidation, destabilizing protein structure, and increasing the susceptibility/sensitivity to elevated temperatures. To counteract the effects of water and limit decomposition; antibodies require constant refrigeration during storage/handling/transport in order to preserve structure, specificity, functionality, and biological activity. As a result, the need for cold chain logistics is a major barrier in resource limited settings; as well as for military medvac operations where equipment weight and accessibility are major tactical concerns. The exclusion of water from antibody preparations is highly appealing and potentially offers a means towards enabling refrigeration-free storage and handling. Antibody nanoscale ionic liquids represent new multifunctional systems that are well suited towards addressing these challenges. Here, we describe the creation of an ultra-stable antibody ionic liquid that is water-free, resistant to extreme temperatures (200°C), biologically active, exhibits a long shelf-life, and does not require “cold chain” logistics. We have produced antibody ionic liquids against apoferritin, a histidine-rich protein from the malaria parasite Plasmodium falciparum, and hemoglobin. Given the diversity of antibodies, this represents a generalizable approach to creating antibody ionic liquids for virtually any antibody.
12:30 PM - SM8.1.04
Functional Hydrogels and Particles from Crosslinked Polymeric Telechelics
Christian Wischke 1 , Miroslava Racheva 1 2 , Florian Stormann 1 3 , Elen Baehr 1 , Andreas Lendlein 1 2 3
1 Institute of Biomaterial Science and Berlin-Brandenburg Center for Regenerative Therapies, Helmholtz-Zentrum Geesthacht, Teltow Germany, 2 Department of Biology, Chemistry and Pharmacy, Freie Universität Berlin, Berlin Germany, 3 Institute of Chemistry, University of Potsdam, Potsdam Germany
Show AbstractTelechelic polymers can be the basis to construct a large variety of functional materials if combined with both suitable crosslinking techniques and shaping into the desired 3D structures. In this contribution, two examples illustrating the variety of advanced polymeric systems realized from telechelics with distinct endgroups will be given.
Hydrophilic 4-arm star shaped telechelics from poly(ethylene glycol) bearing end groups derived from aromatic amino acids can be substrates of enzymes, thereby allowing an enzymatic catalysis of hydrogel synthesis. Due to the efficiency of the enzymatic reaction, it was envisioned that immobilized enzymes could likewise catalyze such reactions. Here, the surface immobilization of mushroom tyrosinase is reported, which theoretically could allow producing hydrogel coatings at devices of any given shape.
Using polyester telechels with photocrosslinkable end groups, hydrophobic materials can be obtained, which also can be structured in the shape of polymer micronetwork particles. Those particles exhibit elasticity allowing deformation and, furthermore, the capacity to actively switch shape [1]. Beyond this, polymer particles with anisotropic shapes as well as particles with expandable volumes will be presented.
[1] Friess F. et al. (2014) Adv Healthcare Mat 3: 1986-1990.
12:45 PM - SM8.1.05
Enzymatic Polymerization of High Molecular Weight ssDNA
Lei Tang 3 , Yaroslava Yingling 2 , Ashutosh Chilkoti 1 , Stefan Zauscher 3
3 Mechanical Engineering and Materials Science, Duke University, Durham, North Carolina, United States, 2 Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina, United States, 1 Biomedical Engineering, Duke University, Durham, North Carolina, United States
Show AbstractThe use of DNA as a polymeric building material transcends its function in biology and is exciting in bionanotechnology for applications ranging from biosensing, to diagnostics, and to targeted drug delivery. Hence, the effectient and precise synthesis of high molecular weight DNA materials has become key to advance DNA bionanotechnology. Current synthesis methods largely rely on either solid phase chemical synthesis or template-dependent polymerase amplification. In contrast, we here exploit the ability of a template-independent DNA polymerase-terminal deoxynucleotidyl transferase (TdT) to catalyze the polymerization of 2’-deoxyribonucleoside 5’-triphosphates (dNTP, monomer) from the 3’-hydroxyl group of an oligodeoxyribonucleotide (initiator). We term this enzymatic synthesis method: TdT catalyzed enzymatic polymerization, or TCEP.
Using in situ 1H NMR and fluorescent gel electrophoresis we found that TCEP kinetics follows a “living” chain-growth polycondensation mechanism, and that like in “living” polymerizations, the molecular weight of the final product is determined by the starting molar ratio of monomer to initiator. We developed a reaction kinetics model that allows us to quantitatively describe the extent of reaction and to predict the molecular weight of the reaction product. We also demonstrate TCEP’s capacity to incorporate a wide range of unnatural dNTPs into the growing chain, such as, hydrophobic fluorescent dNTP and fluoro modified dNTP. Building on TCEP’s synthesis capacities, we invented a two-step strategy to synthesize diblock amphiphilic polynucleotides, in which the first, hydrophilic block serves as a macro-initiator for the growth of the second block, comprised of natural and/or unnatural nucleotides. By tuning the hydrophilic length, we synthesized amphiphilic diblock polynucleotides that can self-assemble into micellar structures ranging from star-like to crew-cut morphologies. The observed self-assembly behaviors agree with predictions from dissipative particle dynamics (DPD) simulations as well as scaling law theory for polyelectrolyte block copolymers. We believe that TCEP advances the synthesis of multifunctional DNA materials, and enables novel applications for this new class of polynucleotide polymers.
SM8.2: Advanced Structured Materials
Session Chairs
Tuesday PM, April 18, 2017
PCC North, 100 Level, Room 124 A
2:30 PM - SM8.2.01
Self-Assembling Nanocomposite Tectons
Robert Macfarlane 1
1 , Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show AbstractNanocomposites consisting of inorganic nanoparticles embedded within a polymer matrix are an important class of materials based on integrating two or more disparate phases to achieve physical characteristics that cannot be realized with a single-phase material. Current syntheses typically focus on chemical composition as the primary factor that determines these properties, but nanocomposite characteristics are also dependent on the geometric arrangement of the phases and the chemical interface between them. While structure control in macroscopic composites can be easily achieved via top-down mechanical processing, similar approaches with nanocomposites either provide limited spatial resolution at the nanometer length scale or are undesirably inefficient. Alternatively, self-assembly could in principle produce polymer-nanoparticle composites with well-defined geometries in a parallelizable manner that is amenable to scale-up. However, the major limitations of current techniques are that they either focus solely on ensuring compatibility of the organic polymer and inorganic nanoparticle phases and lack hierarchical structural organization of all constituent components, or utilize structure-directing agents or processing conditions that are not amenable to functional composite architectures. Here, we circumvent these challenges by developing a new class self-assembling building blocks we term nanocomposite “tectons” (NCTs) – irreducible nanocomposite building blocks that are themselves nanocomposite architectures. An NCT consists of a nanoparticle grafted with polymer chains that terminate in functional groups capable of supramolecular binding, where supramolecular interactions between polymers grafted to different particles enable programmable bonding to drive particle assembly. Importantly, these interactions can be manipulated separately from the identity of the organic or inorganic components of the NCT, allowing for independent control of the chemical composition and spatial organization of all phases in the nanocomposite via a single design concept. The development of NCTs therefore enables the next generation of nanocomposites with simultaneous multi-level structure control to precisely dictate material physical properties.
2:45 PM - *SM8.2.02
Advanced Materials from Polymer Hybrids Self-Assembly
Ulrich Wiesner 1
1 , Cornell University, Ithaca, New York, United States
Show AbstractGlobal problems including energy conversion and storage, clean water and human health require increasingly complex, multi-component hybrid materials with unprecedented control over composition, structure, and order down to the nanoscale. This talk will give examples for the rational design of novel functional polymer hybrid materials inspired by biological examples. These materials are often based on the self-assembly of block copolymers as structure directing molecules for polymer-inorganic hybrid materials. Discussion will include formation of synthetic porous materials with amorphous, polycrystalline, and epitaxially grown single-crystal structures. Experiments will be compared to theoretical predictions to provide physical insights into formation principles. The aim of the described work is to understand the underlying fundamental chemical, thermodynamic and kinetic formation principles enabling generalization of results over a wide class of materials systems. Examples will cover the formation of hierarchical structures at equilibrium as well as via processes far away from equilibrium. Targeted applications of the prepared systems will include the development of fluorescent hybrid probes for nanomedicine, nanostructured hybrids for energy conversion and storage devices, as well as the formation of first self-assembled superconductors.
References
1.) S. W. Robbins, P. A. Beaucage, H. Sai, K. W. Tan, J. P. Sethna, F. J. DiSalvo, S. M. Gruner, R. B. van Dover, U. Wiesner, Block copolymer self-assembly directed synthesis of mesoporous gyroidal superconductors, Sci. Adv. 2 (2016), e1501119.
2.) K. W. Tan, B. Jung, J. G. Werner, E. R. Rhoades, M. O. Thompson, U. Wiesner, Transient Laser Heating Induced Hierarchical Porous Structures from Block Copolymer Directed Self-Assembly, Science 349 (2015), 54-58.
3.) E. Phillips, O. Penate-Medina, P. B. Zanzonico, R. D. Carvajal, P. Mohan, Y. Ye, J. Humm, M. Gönen, H. Kaliagian, H. Schöder, H. W. Strauss, S. M. Larson, U. Wiesner, M. S. Bradbury, Clinical translation of an ultrasmall inorganic optical-PET imaging nanoparticle probe, Sci. Transl. Med. 6 (2014), 260ra149.
4.) H. Sai, K. W. Tan, K. Hur, E. Asenath-Smith, R. Hovden, Y. Jiang, M. Riccio, D. A. Muller, V. Elser, L. A. Estroff, S. M. Gruner, U. Wiesner, Hierarchical porous polymer scaffolds from block copolymers, Science 341 (2013), 530-534.
3:15 PM - SM8.2.03
DNA-Inspired Self-Assembly of Nanoscale Electronic Devices
Kuo Yao Lin 1 , Jason Slinker 1 , Alon Gorodetsky 2 , Andrew Bartlett 2
1 Department of Physics, University of Texas at Dallas, Dallas, Texas, United States, 2 Department of Chemical Engineering and Materials Science, The University of California, Irvine, Irvine, California, United States
Show AbstractDespite remarkable examples of difficult-to-produce isolated molecular devices, the scalable nanomanufacturing of such electronics remains at a standstill due to fundamental roadblocks associated with the synthesis of large quantities of modular nanoscale circuit elements. We have introduced a methodology for mass production of nanoscale electronic elements. We have synthesized organic semiconductor moieties within DNA-like scaffolds, leveraging the rapid, efficient, and precise coupling afforded by traditional DNA bioconjugate chemistry. These DNA-inspired nanowires enable the self-assembly of active, nanoscale circuit elements at patterned electrodes. The assembly and electrical performance of these arrayed devices have been characterized through scanning microscopy techniques and custom, automated electrical probe measurements. Our unique and economically viable approach offers a new paradigm for the fabrication of nanoscale electronic circuits.
3:30 PM - SM8.2.04
Designing Nanostructured Functional Gels for Smart Electronics and Electrochemical Energy Devices
Ye Shi 1 , Guihua Yu 1
1 , University of Texas at Austin, Austin, Texas, United States
Show AbstractMultifunctional gel materials with responsive properties are becoming critically important for wide ranging technological applications, from electronics, biomedical devices, to electrochemical energy devices. To enable significantly improved or even unprecedented properties and designed new functionalities, the chemical composition, micro/nano-structures and physical interactions of gel materials need to be delicately controlled. Here we will present our representative works on rational design and chemical modification of gels with function-enriched properties and their applications in smart responsive electronics and electrochemical energy devices. We designed hybrid gels with an interpenetrating binary network structure by using conductive gels with hierarchically porous structure as a “host” matrix and introducing second polymers such as PNIPAM and supramolecular gel with distinct functionalities as “guest”. By tuning the interactions between two polymeric networks and chemically modifying the interface, the hybrid gels exhibited tunable chemical/physical properties and attractive synergistic characteristics: high electrical conductivity, enhanced mechanical properties and unique functionalities such as thermo-responsive sensitivity, room temperature self-healing behavior, which were used for building up smart electronics. I will discuss another recent work on developing the smart electrolyte that can respond to temperature change and regulate the motion of ions owing to its reversible sol-gel transition, thus realizing self-regulated electrochemical devices with thermal safety. Our works revealed the fundamental structure-property-function relationship of these multifunctional gel systems, and provided a unique material platform to enable their promising applications in self-healing, adaptive electronics, and thermoresponsive electrochemical devices.
3:45 PM - SM8.2.05
Assembly of Ligand Stripped Nanocrystals of Arbitrary Composition with Block Copolymers in Thin Film at Both Low and High Inorganic Loading Fractions
Gary Ong 2 1 , Brett Helms 3 , Delia Milliron 1
2 Materials Science and Engineering, University of California, Berkeley, Berkeley, California, United States, 1 Chemical Engineering, University of Texas at Austin, Austin, Texas, United States, 3 , Lawrence Berkeley National Laboratory, Berkeley, California, United States
Show AbstractBlock copolymer directed assembly of nanocrystals present an exciting avenue for enabling bottom up processing of inorganic materials and organic-inorganic composites that harness the merits of both classes of materials along with precise control of structure. One limit in the approach include chemical specificity necessitating nanocrystal surface ligand functionalization prior to assembly to prevent macrophase separation of nanocrystals out of the block copolymer domain. A second limit is the ability to achieve a high loading of nanocrystals in the structure without macrophase separation or kinetic arrest due to effects such as particle jamming. By studying a specific polymer polystyrene-polydimethylacrylamide where the acrylamide block preferentially adsorbs to bare nanocrystal surfaces, we demonstrate that we can achieve assembly of nanocrystals of arbitrary composition as long as the nanocrystals are ligand stripped of their native organic ligands. This system enables assemblies with up to 40 volume percent inorganic loading yielding mesoporous structures via micelle templating. Selection of nanocrystal size determines the placement of nanocrystals within the polymer domain, be it close or farther from the diblock interface, as well as the density of particle placement within the block. Furthermore, solvent annealing is used to relax structures into their thermodynamic microphase separated configuration enabling morphological control.
SM8.3: Stimuli-Sensitive Polymers II
Session Chairs
Tuesday PM, April 18, 2017
PCC North, 100 Level, Room 124 A
4:30 PM - SM8.3.01
Onion-Like Multilayered Capsules Based on Stimuli-Responsive Polymers—Synthesis by a Bioinspired “Inside-Out” Technique
Brady Zarket 1 , Srinivasa Raghavan 1
1 Chemical & Biomolecular Engineering, University of Maryland, College Park, College Park, Maryland, United States
Show AbstractDiverse structures in nature such as eggs, embryos, body parts like the spinal disc, plant seeds, and the onion all have a common structural motif, which is the presence of multiple concentric layers. Individual layers are often composed of distinct materials because the layers serve different purposes. The creation of these structures in nature (morphogenesis) typically proceeds by the initial formation of an inner layer or core, followed by a first shell, and a further progression outwards to add more shells. Here, we draw inspiration from natural morphogenesis to create multilayered polymer capsules by an “inside-out” technique. First, an aqueous gel core is loaded with an initiator. This core is placed in a solution of monomer 1, whereupon a shell of polymer 1 grows around the core. Thereafter, this core-shell structure is loaded with fresh initiator and placed in a solution of monomer 2, which causes a concentric shell of polymer 2 to form around the first shell. This process can be repeated further to obtain multiple layers of distinct polymers. Each polymeric shell grows outward from the surface of the previous shell; thus, the thickness of a given shell steadily increases with time and can be controlled. A highlight of this technique is the ability to juxtapose different polymers next to each other among the concentric layers in an onion-like capsule. For example, layers of a non-responsive polymer can be placed next to either a temperature-responsive or a pH-responsive polymer. By varying the location of the stimuli-responsive layer(s), we demonstrate that the release of solutes (e.g., drugs) from the capsule can be made to follow unique multi-step release profiles as the stimulus is varied.
4:45 PM - SM8.3.02
Stimuli-Responsive Coaxial Electrospun Membranes Using Self-Immolative Polymers
Daewoo Han 1 , Xinjun Yu 2 , Qinyuan Chai 2 , Neil Ayres 2 , Andrew Steckl 1
1 Department of Electrical Engineering and Computing Systems, University of Cincinnati, Cincinnati, Ohio, United States, 2 Department of Chemistry, University of Cincinnati, Cincinnati, Ohio, United States
Show AbstractThe first self-immolative polymer (SIP) nanofiber membrane has been demonstrated in this report. SIPs are polymeric linear molecules that respond to external stimuli by undergoing head-to-end depolymerization.1 The triggered unzipping of the polymer backbone allows the release of the small molecules components contained within the initial polymer. Recently, micro-capsules with an SIP shell have demonstrated the triggered release of embedded materials.
Electrospinning is a highly versatile method for creating continuous fibers ranging from tens of nanometers to microns in diameter and many meters in length. This is accomplished by applying a voltage between a droplet at a nozzle tip and a collecting substrate. Under the proper conditions (solution conductivity, viscosity, etc.), the applied electric field causes a liquid jet to eject from the droplet. During this process the jet elongates, ultimately resulting in a non-woven mesh of fibers with very high surface-to-volume ratio. Furthermore, using coaxial electrospinning2, 3, different characteristics from each polymer in different layer can be combined in a single fiber, providing multi-functionality to the resulting membrane. Materials that can combine normally contradictory properties or components can open the door to many exciting new applications.
In this paper, we report on the successful demonstration of coaxial fibers with SIP/PAN sheath and PVP/dye core. Upon the addition of trifluoroacetic acid (TFA) into solutions, SIP is depolymerized and the inner core is exposed to the solution. SEM observation reveals different fiber morphologies before and after triggering reaction in solution. Coaxial fibers show minimal release of the encapsulated core material in non-triggering condition, while instant release of the encapsulated material is observed when the triggering condition is met. The depolymerization time of SIP/PAN blended fiber membranes is ~ 25X quicker than that of cast SIP+PAN films. The surface property of SIP/PAN fiber membranes is switched from hydrophobic (WCA ~ 110°) to hygroscopic (WCA ~ 0°) upon triggered depolymerization, indicating that the sheath layer becomes hygroscopic PAN-rich material by releasing the hydrophobic SIP molecules.
Combining coaxial fibers with stimulus responsive SIPs can provide on-demand (“triggered”) release of, or exposure to, components embedded within the fibers. Also, due to the nature of electrospinning, electrospun SIP membranes have an extremely high surface area, leading to a much faster and more sensitive response to the stimuli involved in polymer self-immolation process. These unique properties will be extremely beneficial for many important applications, such as bio/chemical sensors, drug delivery, catalyst, self-healing, etc.
1. Sagi, A.; Weinstain, R.; Karton, N.; Shabat, D., J. Amer. Chem. Soc. 2008, 130 (16), 5434
2. Han, D.; Steckl, A. J., ACS Appl. Mater. Interfaces 2013, 5 (16), 8241.
3. Han, D.; Steckl, A. J., Langmuir 2009, 25, 9454
5:15 PM - *SM8.3.04
Relations between Response Kinetics and Macromolecular Architecture in Oxidation-Sensitive Materials
Richard d'Arcy 1 , Nicola Tirelli 1
1 NorthWest Centre of Advanced Drug Delivery (NoWCADD), School of Health Sciences, University of Manchester, Manchester United Kingdom
Show AbstractThis paper is about about sulphur(II)-containing polymers, aka polysulfides.
Organic polysulfides have a rich history. Their earliest examples date back to the pioneering age of polymer science: Thiokol A was the first synthetic rubber to be commercialized, well before World War II. More recently (‘60s), the anionic polymerization of episulfides has been a favourite model system during the conceptual development of stereoselective and stereoelective polymerizations. Oblivion then fell on polysulfides until the early 2000s, when the REDOX behaviour of sulphur(II), and specifically its easy oxidizability under mild (and also biologically relevant) conditions paved the way for a renewed interest in these structures. These polymers have then been extensively investigated as materials that exhibit a number of response to biological oxidants (Reactive Oxygen Species, ROS), in particular when the oxidation is linked to significant changes both in the hydrophilicity of the materials and in the morphology of the self-assembled structures they form in water.
In this paper we focus on the relations between macromolecular architecture and oxidative responsiveness. Specifically, we discuss the influence of the polymer primary structure (gradient vs. random structures) and of branching (linear vs. star and comb structures) on the kinetics of the response.
In the first case (primary structure), we have focused on the control of the structure of gradients made of two differently polymerizable monomers, i.e. ethylene sulfide and propylene sulfide; the first one is capable of strong inter- and intramolecular association, in a fashion proportional to the length of its homosequences 1. In the second case (branching), we have compared star and comb polymers (figure on the right) to highlight effects of macromolecular crowding 2.
1. R. d’Arcy, A. Siani, E. Lallana, N. Tirelli “The influence of primary structure on responsiveness. Oxidative, thermal and thermo-oxidative responses in polysulfides”, Macromolecules, 48 (2015) 8108-8120.
2. R. d’Arcy, A. Gennari, R. Donno, N. Tirelli “Linear, star and comb oxidation-responsive polymers: effect of branching degree and topology on aggregation and responsiveness” Macromolecular Rapid Communications, 37 (2016) in press
5:45 PM - SM8.3.05
Photoresponsive Multicompartment Capsules for Controlled Release
Kerry DeMella 1 , Srinivasa Raghavan 1
1 , University of Maryland, College Park, Maryland, United States
Show AbstractPolymer capsules are extensively used in modern times for a variety of applications from cosmetics to biotechnology. The characteristic ability of these structures to encapsulate material and to selectively control permeability and degradation properties utilizing specific external stimuli make capsules an exciting platform for a variety of controlled release applications. For examples, light-sensitive capsules would have applications in a variety of cosmetics formulations. However, most techniques for creating stimuli-responsive polymer capsules require extensive and complex synthesis techniques. Here, we present a quick and simple technique for the synthesis of photoresponsive biopolymer capsules. These photoresponsive biopolymer capsules are synthesized through an electrostatic interaction of a charged biopolymer and a UV-sensitive moiety, creating a robust crosslinked capsule shell. Upon exposure to UV irradiation the UV-sensitive moiety degrades into inert by-products which cannot interact with the biopolymer. As the UV-sensitive moiety degrades the capsule shell weakens, and eventually ruptures, releasing any payload contained within the capsule. Capsule strength and photodegradation time can easily be tuned by altering several parameters such as UV-sensitive molecule concentration, biopolymer molecular weight, and crosslinking time of the capsules. Through manipulation of these parameters we demonstrate these capsules can be utilized as novel vehicles for the controlled and extended release of a variety of payloads.
SM8.4: Poster Session I: Advanced Polymers
Session Chairs
Wednesday AM, April 19, 2017
Sheraton, Third Level, Phoenix Ballroom
9:00 PM - SM8.4.01
Synthesis and Characterization of Photo-Cleavable Nucleotides
Haikang Yang 1 , Anu Stella Mathews 1 , Carlo Montemagno 1
1 , University of Alberta, Edmonton, Alberta, Canada
Show AbstractThis work focuses on the synthesis and chatacterization of eight compounds of 3′-modified-2′-deoxy ribonucleoside triphosphates (dNTPs) for oligonucleiotide custom synthesis. These nucleotide analogues are modified by capping the 3′-OH by a photolabile protecting group which can temporarily cease DNA strand growth and can smoothly reinitiate the growth by photo cleavage of the protecting group and setting the 3′-OH of dNTPs free to propagate. 3′-O-(2-Nitrobenzyl)- 2′ deoxy ribonucleoside triphosphates (NB-dNTPs) and 3′-O-(4,5-Dimethoxy-2-Nitrobenzyl)- 2′ deoxy ribonucleoside triphosphates (DMNB-dNTPs) are the dNTPs synthesised using selective protection strategy. Structural confirmation of the compounds are done by NMR and MS. The UV-cleaving studies of these compounds are monitored and quantified by LC/MS and 1H NMR spectral traces. The synthesized nucleotides are employed for terminating and reinitiating templateless DNA synthesis, using primer indepentent Terminal Deoxynucleotidyl Transferase (TdT) enzyme. These nucleiotides modified at the 3′ hydroxyl position act as template indepentent enzyme mediated oligonucleiotide synthesis terminators, finding immense applications such as DNA synthesis, DNA and RNA 3′ end labelling, mechanistic probes, antimetabolites and antiviral agents paving a novel strategy towards the stacking of dNTPs with the potential to reinforce present technologies.
9:00 PM - SM8.4.02
Highly Specific In Vivo Gene Delivery for p53-Mediated Apoptosis and Genetic Photodynamic Therapies of Tumour
S. Ja Tseng 1
1 , Graduate Institute of Oncology, National Taiwan University College of Medicine, Taipei Taiwan
Show AbstractAnti-cancer therapies are often compromised by non-specific effects and challenged by tumour environments' inherent physico-chemical and biological characteristics. Often, therapeutic effect can be increased by addressing multiple parameters simultaneously. Here we report on exploiting extravasation due to inherent vascular leakiness for delivery of a pH sensitive polymer carrier. Tumours' acidic microenvironment instigates a charge reversal that promotes cellular internalization where endosomes destabilize and gene delivery is achieved. We assess our carrier with an aggressive non-small cell lung carcinoma (NSCLC) in-vivo model and achieve greater than 30% transfection efficiency via systemic delivery. Rejuvenation of the p53 apoptotic pathway as well as expression of KillerRed protein for sensitization in photodynamic therapy (PDT) is accomplished. A single administration greatly suppresses tumour growth and extends median animal survival from 28 days in control subjects to 68 days. The carrier has capacity for multiple payloads for greater therapeutic response where inter-individual variability can compromise efficacy.
9:00 PM - SM8.4.03
Exploring Relaxation Dynamics in Azobenzene Functionalized Polyimides Using Cantilever Bending Experiments and Finite Element Modeling
Matthew Smith 1 , Amir Skandani 2 , David Wang 3 , Loon-Seng Tan 4 , Timothy White 4 , M. Ravi Shankar 2
1 Department of Engineering, Hope College, Holland, Michigan, United States, 2 Department of Industrial Engineering, University of Pittsburgh, Pittsburgh, Pennsylvania, United States, 3 Biological and Nanoscale Technologies Division, UES Inc., Dayton, Ohio, United States, 4 Materials and Manufacturing Directorate, Air Force Research Laboratory, Dayton, Ohio, United States
Show AbstractPhotoisomerization of azobenzene functionalized polymers is a convenient route to transduce light into mechanical work and has been shown to hold promise for a versatile array of programmable materials systems. In particular, azobenzene functionalized polyimides (Azo-PIs) possess several advantages as actuator candidates including exceptional thermal stability, large out-of-plane deformations, and high mechanical strength and stiffness. Generally, the photo-induced deformations in these materials are not fully retained, exhibiting dynamic recovery over time when the light source is removed. In order to tailor Azo-PIs for remotely triggered, fine-tuned actuators and shape memory devices, it is critical to also understand and quantify their relaxation behavior after the light source has been removed. Though studies have investigated the dynamics of strain recovery in azobenzene functionalized polymers after irradiating with UV light, investigations of the relaxation dynamics in Azo-PIs associated with blue-green light remain scarce. Herein, we present results from cantilever bending and relaxation experiments for a series of linear and cross-linked Azo-PIs with varying backbone rigidities. We also use a finite element model that couples population dynamics to material strain to gain insight into the material structure-properties relationships. Ultimately, the goal of this work is to systematically study the strain relaxation dynamics of Azo-PIs after being irradiated by a blue laser (450 nm), and explore the effect of structural parameters - mainly rigidity of polymer backbone molecules - in the short timescale dynamics of polyimides. Control over the persistence and relaxation of photomechanical strains is critical to the broader utility of these materials in shape programmable systems such as those used in the priming of photomechanical actuators and morphing surfaces.
9:00 PM - SM8.4.04
Incorporating Longer Wavelength Azo Dyes in Polymer Networks for Photomechanical Applications
Brandon Derstine 1 , Sean Gitter 1 2 , Jessica Korte 2 , Matthew Smith 2 , Jason Gillmore 1
1 Department of Chemistry, Hope College, Holland, Michigan, United States, 2 Department of Engineering, Hope College, Holland, Michigan, United States
Show AbstractAzo dyes have long been incorporated into photomechanical systems with promise as wireless actuators.[1] Most azo dyes photoisomerize in the ultraviolet to blue/green region of the electromagnetic spectrum. However, these high energy wavelengths often lead to photodegradation of the material. They are also competitively absorbed by other device components. Furthermore, these wavelengths are incompatible with mammalian tissue, thus limiting any potential biomedical applications.
Recently, Aprahamian and coworkers published a series of BF2-coordinated azo dyes which photoisomerize in the red[2] to near-infrared[3] (NIR) region of the spectrum. These lower energy wavelengths minimize absorption by mammalian tissue, photodegradation of the material, and competitive absorption by other device components. In the Gillmore organic photochemistry research group, we are preparing analogs of Aprahamian’s dyes with polymerizable “handles” that may then be incorporated into photomechanical polymers. Meanwhile in the Smith research group in materials science / mechanical engineering, we are developing model polymer systems for the incorporation and characterization of azo dyes in constrained network environments.
Our efforts to date on both fronts and our future plans for this nascent research collaboration are described in this poster.
[1] White, T.J.; Broer, D.J. Nat. Mater. 2015, 14, 1087-1098.
[2] Yang, Y.; Hughes, P.; Aprahamian, I. J. Am. Chem. Soc. 2012, 134, 15221-15224.
[3] Yang, Y.; Hughes, P.; Aprahamian, I. J. Am. Chem. Soc. 2014, 136, 13190-13193.
9:00 PM - SM8.4.05
Continuous Fabrication of Polymeric Microstencil by Using Dewetting Phenomenon
Moonkyu Kwak 1 , Cheol Woo Park 1 , Gyu Man Kim 1 , Jung Goo Hong 1
1 , Kyungpook National University, Daegu Korea (the Republic of)
Show AbstractWe present the continuous fabrication of a polymeric microstencil by using continuously occurring dewetting phenomenon via roll to roll imprinting equipment. To realize dewetting assisted residual free imprinting, mold material, polymer resin and substrate were selected by using interfacial surface energy analysis. In addition, optimal parameters of the continuous process are also explored by systematical investigating the completion of microstencil depending on the process speed, aspect ratio of mold and applied pressure. In the result, the polymeric microstencil was produced continuously with very high yield and its maximum resolution reached to 20 μm in diameter. For the easy continuous demolding during the roll to roll process, the substrate was further chosen with paraffin-coated film (PPF) which has low enough surface energy for dewetting but still has a higher adhesion value than PDMS mold. This versatile, high-throughput microstencil architecturing may be applicable to many applications requiring flexibility, scalability, and specific material, and their commercially-feasible production.
9:00 PM - SM8.4.06
4D Printing Bio Functional Materials
Anu Stella Mathews 1 , Surjith Kumaran 1 , Jiaxin Fan 1 , Sinoj Abraham 1 , Carlo Montemagno 1
1 , University of Alberta, Edmonton, Alberta, Canada
Show AbstractThe transfer of bio functionality from native living organisms to stable engineered environment opens a wide horizon of applications. Our work focus on the creation of materials and devices that transform bio traits and collect, process and act on the information in response to changes in their local environment thus promoting additive manufacturing from 3D space to a four-dimensional, functional space. Through developments in stabilizing fundamental biological building blocks and integral membrane proteins, the suite of tools available to engineer complex systems has been greatly expanded. In this work a new class of light curable bio inks exploits this expanded set of tools to enable the incorporation of biological function as an intrinsic property in the devices we print. This device incorporates bio functions into a new class of engineered structures with high efficiency and purity. We have designed and developed protocol for synthesizing and stabilizing biological molecules out of their living environment, and transferring into 4D printable bioinks. The designed printable bio-inks process the potential of precise heterogeneous assembly attained through the selection of polymers, bio functional moieties and light source. The properties of this 4D printable bioinks are tailored according to the functionality incorporated and the light source used so that the materials can be utilized for fabricating 4D printed systems with potential applications varying from biochemical energy harvesting devices to scaffolds for biomedical engineering.
9:00 PM - SM8.4.07
Advancing the Knowledge on the Structural Properties of the Biocompatible and Biodegradable Electroactive Eumelanin Polymer
Dominic Boisvert 1 , Carmela Prontera 3 2 , Sebastien Francoeur 1 , Antonella Badia 1 , Clara Santato 1
1 , Polytechnique Montréal, Montreal, Quebec, Canada, 3 , Enea Research Center, Roma Italy, 2 , University of Naples Federico II, Napoli Italy
Show AbstractEumelanin is a dark-brown biopigment largely present in animals and plants. This biopolymer results from the polymerization of two monomers (building blocks), namely 5,6-dihydroxyindole (DHI) and 5,6-dihydroxyindole-2- carboxylic acid (DHICA) [1]. Important physicochemical properties of eumelanin include metal chelation, photoprotection (the pigment absorbs in the nearIR – UV region of the spectrum) and mixed ionic-electronic conduction. It also features biocompatibility and biodegradability [2]. Although eumelanin has been studied for a few decades now, the nature of its chromophoric units and the mechanism of charge carrier transport are still largely undiscovered, mainly because of the chemical disorder that characterizes natural eumelanin. Obtaining a good control over the molecular and supramolecular structures of the pigment is therefore imperative to achieve better understanding of those properties, a key to demonstrate eumelanin-based environmentally and human-friendly technologies.
Here we report on the controlled polymerization in films of DHI building blocks spin coated on SiO2 and quartz substrates, observed in situ by Atomic Force Microscopy (AFM). DHI films obtained from methanol solutions of freshly synthesized DHI, were polymerized in ambient conditions (oxidative polymerization). A number of factors likely contribute to establishing the mechanism of polymerization. Besides molecular oxygen, monomer/oligomer aggregates in the methanol suspensions can act as nuclei of the polymerization. Our preliminary results suggest that the physical contact between the AFM tip and the monomers/oligomers plays a role in triggering the polymerization. Once started, the polymerization front develops within a time scale of minutes on a preferential direction, creating elongated, dendritic structures, leading to furrow-like surfaces, separated by a few micrometers. The dendrimers, carefully characterized by AFM, were also investigated by spatially resolved absorption spectroscopy. The large scale, directional and dendritic polymerization can be exploited to obtain chemically controlled eumelanin samples that can be efficiently characterized for their optical and transport properties and, on the long term, exploited in organic electronics devices, such as transistors and solar cells. Further studies on the polymerization in the presence of metallic substrates or metal ions will provide insight on the effect of metal chelation on the polymerization patterns, thus giving more insight for future melanin-based devices.
[1]
M. D'Ischia, et. al., "Melanins and melanogenesis: methods, standards, protocols," Pigment Cell & Melanoma Research, vol. 26, no. 5, pp. 616-633, 2013.
[2]
C. J. Bettinger, et. al., "Biocompatibility of biodegradable semiconducting melanin films for nerve tissue engineering," Biomaterials, vol. 30, no. 17, pp. 3050-3057, 2009.
9:00 PM - SM8.4.08
Fluorescent Potassium Ion Sensors
Yanqing Tian 1
1 Department of Materials Science and Engineering, South University of Science and Technology of China, Shenzhen, Guangdong, China
Show AbstractPotassium ions which make up about 0.4% of the mass in the human body and are the most abundant intracellular cation, play diverse roles in biological processes including muscle contraction, heartbeat, nerve transmissions, and kidney functions. Abnormal K+ fluctuations are early indicators of diseases such as alcoholism, anorexia, bulimia, heart disease, diabetes, AIDS, and cancer. Therefore the detection of K+ in physiological environment is of great significance. One of the earliest and best-known intracellular fluorescent K+ probes is potassium-binding benzofuran isophthalate (PBFI), which uses a diaz-18-crown-6 as a ligand and a benzofuran derivative as the fluorophore. Unfortunately PBFI, suffers poor selectivity for potassium ions with respect to sodium ions (Na+). Herein, we will describe our results for developing highly selective potassium ion sensors. We used triazacryptand (TAC) as a high selective potassium ion ligand and various fluorophores for preparing highly selective potassium molecular and planar polymeric probes. We constructed a potassium ion sensor using a 2-dicyanomethylene-3-cyano-4,5,5-trimethyl-2,5-dihydrofuran (TCF) as a strong electron withdrawing group and the TAC as the electron donating group for the first intracellular potassium ion sensor. Later we incorporated a triphenylphosphonium (TPP) unit into a BODIPY fluorophore with TAC as the ligand for the first mitochondrial targeting potassium ion probe. These two molecular probes show high selectivity for potassium ions and capable for monitoring intracellular potassium fluxes. Especially the probe with TPP moiety showed high co-localization efficiency for mitochondria. We also prepared a polymerizable potassium ion probe using naphthalimide as the fluorophore for generation of planar thin film-based potassium ion sensors. These polymeric sensors showed potassium ion dynamic response ranges from 1 to 20 mM, indicating its suitableness for extracellular sensing. This sensor also has a minimum influence by pH from 6 to 8, showing its suitableness for biostudies. We tested whether this sensor can be used to monitor extracellular potassium ion concentration changes. We used lysozyme to kill bacteria (E. Coli and B. Subtilis) to release their cellular potassium ions to the media to enable us to monitor potassium concentration changes in real time. Results showed that potassium ion concentration is higher with higher cell densities. We also found the difference among the two species of cells. E coli release potassium ions much slower than that Subtilis did. Thus in this presentation, we will give detailed results about our potassium ion sensors.
9:00 PM - SM8.4.09
Nanodiamond-Embedded Polymeric Thermogels and Hydrogels—Properties and Applications
Kangyi Zhang 1 , Sing Shy Liow 1 , Zhi Wei Low 1 , Anis Abdul Karim 1 , Xian Jun Loh 1 2 3
1 , Institute of Materials Research and Engineering, Singapore Singapore, 2 Materials Science and Engineering, National University of Singapore, Singapore Singapore, 3 , Singapore Eye Research Institute, Singapore Singapore
Show AbstractNanodiamonds (NDs) have emerged as an attractive candidate for biomedical applications such as imaging and drug delivery. Clinical relevance has been shown in many recent studies such as for therapeutic contact lenses, implantable drug-eluting hydrogels and anti-bacterial tooth fillings. NDs are highly biocompatible and amenable to surface modifications for different purposes. Nanodiamonds have previously been shown to enable targeted delivery of chemotherapeutics and the stable delivery of hydrophobic drugs and genetic material. Beyond drug delivery, nanodiamonds can also act as nanofillers to strengthen hydrogels for structural support. The mechanical properties are highly tunable and the improved strength makes them attractive for different tissue engineering scaffolds.
Our lab has previously developed polyurethane-based thermogels which can be used for healthcare and personal care applications. Our polyurethane thermogel is capable of gel formation at low polymeric concentrations and allows for reversible sol-gel transitions. Compared to poly(N-isopropylacrylamide) (PNIPAAm) systems, our thermogel is biodegradable and will not require any surgery to remove the gel after utilization. Delivery of active ingredients can be done in a single injection and the in situ gelation will enable a localized and sustained drug delivery.
After nanodiamond incorporation into the thermogels, reversible sol-gel transition was unaffected. Our system retained high encapsulation efficiency of both hydrophobic and hydrophilic actives. We studied this gelation phenomenon over various concentrations of NDs. Rheology and other characterization will be discussed. Cell biocompatibility tests will also be presented to show the biological feasibility of this system. We envision this biocompatible and biodegradable system to be highly versatile in delivering therapeutics with high efficiency. A range of healthcare and personal care applications can be explored.
9:00 PM - SM8.4.10
Controlling the Pore Size of Mesoporous Carbon Thin Films through Thermal and Solvent Annealing
Guoliang Liu 1 , Zhengping Zhou 1
1 , Virginia Polytechnic Institute and State University, Blacksburg, Virginia, United States
Show AbstractWe describe an approach to controlling the pore size of mesoporous carbon thin films from metal-free polyacrylonitrile-containing block copolymers. A high-molecular-weight poly(acrylonitrile-block-methyl methacrylate) (PAN-b-PMMA) was synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization. We systematically investigated the self-assembly behavior of PAN-b-PMMA thin films during thermal and solvent annealing, as well as the pore size of mesoporous carbon thin films after pyrolysis. The as-spin-coated PAN-b-PMMA microphase-separated into uniformly spaced globular nanostructures, and these globular nanostructures evolved into various morphologies after thermal or solvent annealing. Surprisingly, through thermal annealing and subsequent pyrolysis of PAN-b-PMMA into mesoporous carbon thin films, the pore size and the center-to-center spacing of pores increased significantly with annealing temperature, different from most block copolymers. In addition, the choice of solvent during solvent annealing strongly influenced the block copolymer nanostructures and the pore size of mesoporous carbon thin films. The discoveries herein provide a simple strategy to control the pore size of mesoporous carbon thin films by tuning thermal or solvent annealing conditions, instead of synthesizing a series of block copolymers of various molecular weights and compositions.
9:00 PM - SM8.4.11
Long-Range Ionic Conductivity of Saturated Bacterial Cellulose-Based Solid Biopolymer Electrolyte Offers Insights into the Transport Mechanism of Bulk Nanofibers
Robert Ccorahua 1 , Omar Troncoso 1 , Fernando Torres 1
1 , Pontificia Universidad Catolica del Peru, LIMA Peru
Show AbstractThe study of electrically conductive bionanocomposites has attracted scientific interest due to the increasing demand of new technologies for the development of bioelectronic devices such as biointerface materials and biosensors. In this context, bacterial cellulose nanofibers (BC) appears as a promising supporting material for conductive additives due to its high strength and stiffness, renewability, biocompatibility and biodegradability.
Complexed bacterial cellulose-potassium iodide (BC-KI) films were prepared by dipping BC films in solutions of KI at different concentrations. Impedance spectroscopy tests were carried out and the imaginary part of the electric modulus (M’’), impedance (Z’’) and dielectric loss (ε’’) were plotted as functions of frequency (f). The dielectric data were also utilized to calculate the coefficient of ionic diffusivity using a model proposed by Bandara & Mellander.
The results showed that the highest ionic conductivity (1x10-5 S/cm) was achieved for the specimens with the highest KI content (BC-KI 91%). In addition, the analysis of the M’’ and ε’’ spectra suggests that the dielectric response of the material is mainly due to delocalized (long-range conductivity) ion motion. A single peak in the M’’ spectra suggests that the ionic and polymer segmental motion is strongly coupled. In addition, the increase on the salt content promoted the long-range random hopping movement of ions, even at high frequencies (1 MHz). The high coefficient of ionic diffusivity (8.01 x 10-3 cm2/s) of the BC-KI samples with content of 89% of KI would be due to the large surface area of BC nanofibers.
In conclusion, the high conductivity, dominated by long-range random hopping ion motion, and high diffusion coefficient of saturated BC could open new windows for its use in solid energy and biointerface devices.
9:00 PM - SM8.4.12
Ultrasonic Cavitation Induced Shape-Memory Effect in Porous Polymer Networks
Pengfei Zhang 1 2 3 , Marc Behl 1 3 , Xingzhou Peng 1 2 3 , Muhammad Yasar Razzaq 1 , Andreas Lendlein 1 2 3
1 , Institute of Biomaterial Science and Berlin-Brandenburg Centre for Regenerative Therapies, Helmholtz-Zentrum Geesthacht, Teltow Germany, 2 , Institute of Chemistry, University Potsdam, Potsdam Germany, 3 , Tianjin University-Helmholtz-Zentrum Geesthacht Joint Laboratory for Biomaterials and Regenerative Medicine, Teltow Germany
Show AbstractUltrasound is an efficient tool to generate local mechanical force in liquid media by cavitation.[1,2] The application of cavitation-based mechanical forces (CMF) has evolved as a valuable technology to increase the skin permeability, or to enhance the drug delivery efficiency to targeted tissues. Inspired by the usage of CMF in natural soft materials and the demand to implement other stimuli than heat into shape-memory polymers, we explored whether a polymer network can be created, which is capable to change its shape when CMF are applied. As the ultrasonic cavitation occurs dominantly at the surface of solid polymers, a key challenge was the design of an appropriate material structure, which enables the CMF to effectively permeate throughout the bulk polymer sample. In addition, the selection of suitable molecular switches (temporary crosslinks) was a critical issue as well. The molecular switches must exhibit mechano-responsivity to enable the shape recovery during sonication but also need to provide a certain stability for fixing the temporary shape. We addressed these challenges by the design of a rhodium-phosphine interconnected macro-porous polymer network (Rh-IMP).[3] To synthesize Rh-IMP, n-butyl acrylate and diphenylphosphinostyrene (DPPST) were copolymerized in the presence of poly(propylene glycol) dimethacrylate crosslinker. Here, poly(n-butyl acrylate) was employed as the compound for the elastic polymer backbone, while DPPST was helpful to establish rhodium-phosphine coordination bonds by the addition of [RhCl(COD)]2. The rhodium-phosphine coordination bonds (Rh-PCBs) and their separated micro-phases act as temporary crosslinks in Rh-IMP. Rheology measurements indicated a decrease in storage moduli (G′) of the Rh-IMP, originally ranging from 62 to100 kPa to 30-58 kPa after sonication (US, f =20 kHz). After removal of US, the values of G′ displayed a reversible increase and reached equilibrium after 6 hours, thus verifying the reversible dissociation of the aggregates of the micro-phase separated morphology in Rh-IMP. In this way, the ligand exchange of Rh-PCBs in the polymer network is accelerated, resulting in a topological rearrangement of molecular switches. This rearrangement of molecular switches enables the Rh-IMP with a CMF-induced shape-memory effect with the shape-fixity ratio in a range from 43 to 93% and shape-recovery ratio ranging from 43 to 97% for samples differing in DPPST mole ratios. The interconnected macro-porous structure with thin pore walls is essential for allowing the CMF to effectively permeate throughout the polymer network. Potential applications of this CMF-induced shape-memory polymer could be mechano-sensors or ultrasound controlled switches.
References
[1] D. G. Shchukin, E. Skorb, V. Belova, H. Mohwald, Adv. Mater. 2011, 23, 1922.
[2] S. Mitragotri, D. Blankschtein, R. Langer, Science 1995, 269, 850.
[3] P. Zhang, M. Behl, X. Peng, M. Razzaq, A. Lendlein, Macromol. Rapid Commun. DOI: marc.201600439R1.
9:00 PM - SM8.4.13
Surface Functionalization and Finishing of 3D Printed Objects with Inkjet Printing and Nanoimprint Lithography
Anita Fuchsbauer 1 , Michael Muehlberger 1 , Helene Ausserhuber 1 , Michael Haslinger 1 , Thomas Lederer 1
1 , Profactor GmbH, Steyr-Gleink Austria
Show AbstractAdditive manufacturing [1] is a term that sums up different technologies that all have in common that the object to be built is generated in a layer-by-layer fashion making it possible to create objects with high geometrical complexity. Furthermore, each fabricated object can be different from the previous one. In order to apply functionalization and surface finishing on top of such objects technologies are needed that can cope with different and varying topologies. Inkjet printing seems to be especially favorable here as it allows the contact free deposition of different types of materials at an exact position onto substrate and can thus be used to create micro- and macrostructures. Inkjet printing is by far not limited to graphical paper printing [2] any more, but is used in printed electronics (like PCB [3], solar cells [4], …), display printing (e.g. PLED [5]) and several other areas. Additional functionalities can be obtained by Nanoimprint Lithography (NIL), especially if the imprint material is inkjet printed and the stamp is flexible. In order to combine AM, inkjet printing and NIL two major topics have to be addressed: (a) inkjet inks with suitable formulations for NIL and (b) inkjet printing on substrates with different topologies. In order to develop inkjet inks suitable for multilayer printing as well as for NIL different commercial available materials from micro resist technology GmbH [6] were investigated and further adapted. Parameters like printhead – substrate distance were investigated and found essential in this field. Further challenges in this field are coping with rough 3D printed surfaces, finding the right spot on the 3D-printed object and adjusting the printhead-substrate distance above a complex surface. We will show possibilities and concepts how to address those issues, using flexible stamps to perform NIL on 3D printed objects, inkjet printing to apply the imprint material on the right spot and 3D machine vision in combination with robotics to position the printhead above the 3D-printed surface
The authors acknowledge funding from Austrian Ministry for Transport, Innovation and Technology (bmvit, ANIIPF project) and the Austrian Research Promotion Agency (FFG, Addmanu project) Furthermore, this work partly funded by the FTI project “ProTechLab”(funded by means of the strategic economy and funding program “Innovatives OÖ2020”)
[1] Guo, N., et al., Front. Mech. Eng. 8 (2013), 215.
[2] C. Williams, Phys. World, 19 (2006) 24–29
[3] C.-W. Wang, W.-C. Chen, K. Cheng, L. Yuh-Zheng, International Conference on Digital Printing Technologies, Portland, (2007), 855–858.
[4] A. Fuchsbauer, J. Kastner, B. Unterauer, M. Wagner, F. Tomarchio, N. Decorde, A. Ferrari, I. Gnatiuk, D. Holzinger, MRS Fall Meeting 2015, BB6.01
[5] F. Dijksman, P. C. Duineveld, M. J. J. Hack, A. Pierik, J. Rensen, J.-E. Rubingh, I. Schram, and M. M. Vernhout, J Mater Chem, 17 (2007), 511 – 522
[6] http://www.microresist.de/
9:00 PM - SM8.4.14
Super Stretchable Gas Barrier of Hydrogen-Bonded Multilayer Nanobrick Wall Thin Films
Shuang Qin 1 , Yixuan Song 1 , Michael Floto 1 , Jaime Grunlan 1
1 , Texas A&M University, College Station, Texas, United States
Show AbstractPackaging of food, pharmaceuticals and electronics often requires gas barrier layers to protect against oxidative degradation. In many cases, during processing or use, the packaging can be subjected to significant strain, so stretchable gas barrier coatings that can maintain high barrier are highly desirable. Layer-by-layer deposition of polymer/clay thin films from water has been shown to produce ‘super’ gas barrier layers, with permeability lower than inorganic oxide or metalized thin films, but these films often crack when stretched more than 5%. Hydrogen-bonded multilayer assemblies, such as poly (ethylene oxide) (PEO)/poly (acrylic acid) (PAA), exhibit high stretchability, but have much higher oxygen permeability (yielding only a 10X barrier improvement on 1.6 mm natural rubber). Here we show how montmorillonite (MMT) clay platelets were incorporated into the PAA solution to prepare PEO/PAA+MMT multilayer thin films. Highly aligned platelets are observed in these films and improved the oxygen transmission rate (OTR) by a factor of 10 relative to PEO/PAA previously reported (when deposited on a 1mm thick polyurethane rubber). A 10-bilayer (432 nm thick) PEO/PAA+MMT film has an OTR (1.74 cc /m2*day*atm) that is two orders of magnitude lower than the polyurethane rubber substrate. When multiplied by thickness, the calculated coating permeability is 1.5*10-15 cm3*cm/ (cm2*Pa*s), which is five orders of magnitude lower than the substrate. This film maintains its inherit stretchability from PEO/PAA and maintains its high barrier at 20% strain. This is the best stretchable gas barrier ever reported, making these films ideal for applications such as pressurized devices that use elastomeric components.
9:00 PM - SM8.4.15
Highly Stretchable Electrical Conductive Composites Fabricated from Conducting Polymer Networks and Silver Nanostructures for Wearable Electronics
Bo Song 1 , Kyoung-sik Moon 1 , CP Wong 1
1 , Georgia Institute of Technology, Atlanta, Georgia, United States
Show AbstractFuture wearable and portable electronic devices have promoted the research for novel stretchable electrically conductive composites (SECC) in advanced interconnect technology. Currently, challenges remain for the practical application of SECC, including the requirements for ultra-low resistivity (~10-5 Ω cm) for faster operation, the sufficient stretchability to withstand strains for human’s movement (~55%), and retaining electrical properties after mechanical cycles. New materials designs via the shape engineering of conductive fillers and tuning the polymer matrix provide feasible solutions to address the technical challenges.
Here we report a novel approach to fabricate polyurethane (PU)-based SECC by incorporating binary silver-based conductive fillers into a conductive polymer engineered elastomer matrix. The engineering of the conductive polymer resins includes the synthesis of PU elastomer and embedding PU-compatible conductive polymers. The synthesized PU delivered very high mechanical strains over 1000% with small hysteresis. The PU also showed a large volume shrinkage during curing process and soft segments containing polyols can efficiently reduce the organic surfactant on Ag, providing a resistivity 20 times lower than that of PDMS-based SECC. The conductive polymer used, polyaniline (PANI), takes advantage of the acid doping chemistry to control the electrical conductivity, free-volume, and solubility. In contrast to the bulk PANI particles, the nanostructured PANI fibers (~60 nm in diameter, 1-2 µm in length) were synthesized via interfacial polymerization with higher surface area and greater sensitivity towards electrical/mechanical signals. The camphorsulfonic acid was chosen as the dopant to improve the counter ion induced processibility of the PANI, making it highly compatible with the swelled PU in solution. The PU/PANI hybrid matrix has achieved a percolation threshold with less than 10 wt% of PANI loading, while maintaining good stretchability.
Regarding the filler engineering, the 1D silver nanowires (Ag-NWs) and 2D silver microflakes (Ag-MFs) were used as the binary filler systems. Due to the higher aspect ratio, the Ag-NWs can be electrically conductive at a relatively lower percolation threshold in a polymer matrix. To prepare the Ag-NWs, the polyol process was employed using poly(vinylpyrrolidone) as the capping agent and ethylene glycol as the solvent at low temperature (130°C). The synthesized Ag-NWs had an average diameter of 200 nm and the length of 30-40 µm. When using with the silver Ag-MFs, the Ag-NWs could efficiently bridge the flakes and create more conductive channels. The SECC consisting PU/PANI matrix and binary Ag fillers achieved ultra-low resistivity of 1×10-4 Ω cm at 50 wt% of filler loading. In particular, the incorporation of conductive elements in the polymer matrix and the use of high aspect-ratio Ag-NWs (~200) greatly improved the electrical performance under and after the mechanical strains.
9:00 PM - SM8.4.16
Matrix Regenerative Polymer Nanoparticles to Improve the Tumor Microenvironment in Non-Small Cell Lung Cancer
Dhruv Seshadri 1 2 , Andrew Shao 1 2 , Anand Ramamurthi 2 3
1 Department of Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio, United States, 2 Lerner Research Institute, Department of Biomedical Engineering, Cleveland Clinic, Cleveland, Ohio, United States, 3 Department of Molecular Medicine, Cleveland Clinic Lerner College of Medicine of Case Western Reserve University, Cleveland, Ohio, United States
Show AbstractNon-small cell lung cancers (NSCLCs) are a leading cause of mortality in the Unites States with >66% of patients at an advanced stage with a 15% survival rate. Cytotoxic treatments are ineffective due to genetic alterations in tumor suppressor genes. New immune-checkpoint inhibitors targeting the PD1/PD-L1 pathway are promising to treat NSCLCs but response rates are poor (15-20%), motivating need for adjuvant approaches. This has been attributed to the Tumor Micro Environment (TME) which favors immune evasion and pro-tumorigenic pathways such as macrophage polarization from a pro-inflammatory (M1) type to an immunosuppressive and pro-tumorigenic (M2) phenotype. In > 90% of NSCLC patients, the TME is also compromised by secondary COPD, with chronic breakdown of alveolar elastic structures to generate elastin peptides (ELPs), which in turn promote macrophage polarization to the M2 phenotype. Preventing elastolysis and stimulating elastic fiber regenerative repair can thus benefit anti PD1/PDL1 therapy outcomes. This is however severely challenged by inherently poor elastogenicity of adult cells. In this work, we have thus investigated a multipronged approach to NSCLC therapy based on tumor-localized nanoparticle (NP)-based release of doxycycline, which has been shown to inhibit M1 to M2 phenotypic switch and which we have determined to have both anti-proteolytic and pro-elastogenic effects in the 10-20 μM dose range. The biodegradable poly(ethylene glycol)-poly(lactic glycolic acid) (PEG-PLGA) NPs were surface functionalized with a cationic amphiphile. The size of our NPs (200-300 nm) prevented their ready clearence by the RES and ensured minimal phagocytosis. Steady state release of DOX from the NPs depended on DOX loading and NP concentration, but was in the useful low micromolar dose range; at 20 days, only ~28% of theoretically loaded DOX had been released. The cationic amphiphiles on the NPs augmented the effects of the released drug in reducing ELP generation via protease inhibition, and stimulating elastin precursor synthesis and crosslinking. Pendant IL4-receptor (IL4R) antibodies on the NP surface enabled targeted binding to IL4R-expressing M1 macrophages and blocked IL4-induced polarization. In ongoing work, we are investigating in cell culture models, utility of the NPs in inhibiting M1 to M2 phenotypic switch of alveolar macrophages and efficacy of targeting our IL4R Ab-modified NPs to the tumor microenvironment in a C57BL6 mouse tumor model
9:00 PM - SM8.4.17
Cyclodextrin Stabilised Emulsions, Cyclodextrinosomes and Cyborg Cells
Baghali Mathapa 1 , Vesselin Paunov 1
1 School of Mathematics and Physical Sciences (Chemistry), University of Hull, Hull United Kingdom
Show AbstractWe explored the self-assembly of cyclodextrins (CDs) at the oil-water interface through the formation of inclusion complexes (ICs) with the oil and further assemble into microcrystals at the oil-water interface [1-4]. We demonstrate the spontaneous formation of a dense layer of adsorbed CD-tetradecane IC microcrystals at the tetradecane-water interface whose morphology and size are dependent on the type of CD and oil used. At large oil volume fractions, this phenomenon led to the formation of a Pickering type of oil-in-water emulsion stabilised by adsorbed CD-oil microcrystals while at low oil volume fractions it completely solubilises the oil in the form of IC microcrystals. We also report the preparation of o/w emulsions stabilised by microcrystals of cyclodextrin-oil inclusion complexes. The inclusion complexes are formed by threading cyclodextrins from the aqueous phase on n-tetradecane or silicone oil molecules from the emulsion drop surface which grow further into microrods and micro-platelets depending on the type of cyclodextrin. These microcrystals remain attached at the surface of the emulsion drops and form densely packed layers. The novelty in this emulsion stabilisation mechanism is that molecularly dissolved cyclodextrin from the continuous aqueous phase is assembled into colloid particles directly onto the emulsion drop surface, i.e. molecular adsorption leads to effective Pickering stabilisation. The β-CD stabilised tetradecane-in-water emulsions were so stable that we used them as templates for preparation of cyclodextrinosomes after the removal of the core oil (Fig. 1). We also report the preparation of CD-stabilized emulsions with a range of other oils and studied the effect of the salt concentration in the aqueous phase, the type of CD and the oil volume fraction on the type of emulsion formed. The CD-stabilized emulsions and cyclodextrinosomes can find applications in a range of surfactant-free formulations in cosmetics, home and personal care, and in pharmaceutical formulations as drug delivery vehicles. We describe two alternative methods for surface functionalisation of living cells with cyclodextrin molecules without affecting the cell viability [5]. Living cells functionalised with CDs may find many potential applications as they can be loaded with drugs, immunosuppressants and other molecules forming inclusion complexes with their cyclodextrin interface.
[1] B.G Mathapa, V.N. Paunov, J. Mater. Chem. A, 2013, 1, 10836.
[2] B.G Mathapa, V.N. Paunov, PCCP, 2013, 15, 17903.
[3] B.G Mathapa, V.N. Paunov, Soft Matter, 2013, 9, 4780.
[4] B.G Mathapa, V.N. Paunov, J. Mater. Chem. B, 2013, 1, 3588.
[5] B.G Mathapa, V.N. Paunov, Biomaterialce Sci., 2014, 2, 212.
9:00 PM - SM8.4.18
Laser Direct-Write Fabrication of Core-Shell Microspheres
Benjamin Vinson 1 , Samuel Sklare 2 , Jayant Saksena 3 , Douglas Chrisey 2
1 Bioinnovation Program, Tulane University, New Orleans, Louisiana, United States, 2 Physics and Engineering Physics, Tulane University, New Orleans, Louisiana, United States, 3 Biomedical Engineering, Tulane University, New Orleans, Louisiana, United States
Show Abstract
Hydrogel microspheres have found extensive application in tissue engineering and drug delivery for their ability to encapsulate, culture, and/or transport cells, drugs, and other materials in a facile manner. In particular, core-shell microspheres with controlled ECM internal compartments allow for efficient, scalable, and customizable 3D cell culture. However, traditional microsphere fabrication methods provide limited control of core-shell microsphere size and spatial placement. High levels of spatial specificity, reproducibility, and viability have been previously reported using laser direct write (LDW) to print both cells and microspheres. Thus, to overcome these limitations, we show size and spatial control of core-shell alginate microspheres by using the LDW fabrication technique. Our findings show that sphere size is controllable within 10%, and fabricated microbeads can remain immobilized within 5% of their target placement. Demonstration of this technique using the human breast cancer cell line, MDA-MB-231, shows that cells encapsulated within either layer survive at a rate of >85%. Herein we demonstrate LDW’s ability to fabricate and systematically deposit core-shell microspheres into spatially-ordered patterns, with single-microsphere resolution.
9:00 PM - SM8.4.19
Target-Specific Therapeutic Cell Delivery Systems Using Hyaluronic Acid Derivatives
Yun Seop Kim 1 , Sei Kwang Hahn 1
1 Department of Materials Science and Engineering, Pohang University of Science and Technology, Pohang Korea (the Republic of)
Show AbstractHyaluronic acid (HA) is a biodegradable, biocompatible, non-immunogenic, ubiquitous, and naturally occurring linear polysaccharide. There are many kinds of HA receptors in the body, which have been exploited as target sites for HA-based drug delivery systems. Especially, hyaluronan receptor for endocytosis (HARE) and cluster of differentiation 44 (CD44) exist abundantly on liver and tumor, respectively. Mesenchymal stem cells (MSCs) have been widely explored for innovative cell therapies due to their ability to differentiate into diverse lineages and secrete a variety of favorable cytokines. However, migration of MSCs to the target site in most MSC therapies depends on the innate characteristics of MSCs such as the homing ligands of MSCs, resulting in long delivery time and low therapeutic efficacy. Here, we exploited HA for the target-specific delivery of therapeutic MSCs. We conjugated N-terminal amine group of wheat germ agglutinin (WGA) to aldehyde-modified HA for the surface modification of MSCs. WGA is a protein which can specifically recognize sialic acid and N-acetyl-D-glucosamine. The successful synthesis of HA-WGA conjugate was confirmed by gel permeation chromatography, circular dichroism, and Bradford assay. The cytotoxicity of HA-WGA conjugate and the incorporation of HA-WGA conjugate into the cellular membrane of MSCs were assessed by MTT assay and confocal microscopy. After surface modification of MSCs with HA-WGA conjugate, the bio-distribution of MSCs/HA-WGA conjugates after MSCs administrations through various routes was investigated via an IVIS® imaging system and a fluorescence microscope. We will discuss the feasibility of the target-specific MSC therapy for the treatment of liver diseases and cancers.
9:00 PM - SM8.4.20
Nanomechanical Behavior of Clay and Graphene Reinforced Polymers Multilayers
Mohammad Humood 1 , Shuang Qin 1 , Yixuan Song 1 , Jaime Grunlan 1 , Andreas Polycarpou 1
1 , Texas A&M, College Station, Texas, United States
Show AbstractPolymer nanocomposites are useful for many applications such as food packaging and flexible electronics due to their unique characteristics. These hybrid materials usually consist of a polymer matrix and reinforcement (e.g. clay or graphene oxide). Multilayer thin films were synthesized using the layer-by-layer (LbL) assembly method with different layer arrangements, thickness and composition. The simplicity and versatility of the LbL assembly method is due to its flexible water-based process. For packaging, durability is an important feature for these multilayer films, which requires resistance to abrasion in order to maintain the films’ functionality. Some applications are operated by means of mechanical contact such as touch screens and flat panel displays. In order to evaluate the mechanical properties, low and high load nanoindentation, and low and high load scratch experiments were performed. Clay and graphene based multilayers respond differently to applied load. Clay based multilayers, such as montmorillonite (MMT) and polyethylenimine (PEI) bilayers, have exceptional mechanical behavior and scratch resistance. These coatings exhibit high hardness and reduced elastic modulus, smooth surface and low friction. Graphene based multilayers show strong mechanical properties and effective load transfer in the normal direction, but these films show lower resistance to lateral forces compared to polymer/clay assemblies. The graphene/polymer multilayer films suffer from higher friction coefficient, more visible/wider scratches and lower elastic recovery. To improve the scratch resistance of these films, two extra processing steps were introduced: graphene oxide conversion to graphene and polymer crosslinking. These steps improved scratch resistance.
Symposium Organizers
Andreas Lendlein, Helmholtz-Zentrum Geesthacht
Kevin Cavicchi, University of Akron
LaShanda Korley, Case Western Reserve University
Bernd Rehm, Massey University
Symposium Support
MedShape, Inc.
MilliporeSigma
SM8.5/NM10.4: Joint Session: Functional Materials for Cellular and Biotechnological Applications
Session Chairs
Xiaodong Chen
Jianping Fu
Andreas Lendlein
Wednesday AM, April 19, 2017
PCC West, 100 Level, Room 102 AB
9:30 AM - SM8.5.01/NM10.01
Regulation of Mesenchymal Stem Cell Behavior and Secretion via Microscale Surface Roughness
Nan Ma 1 , Xun Xu 1 , Weiwei Wang 1 , Zhengdong Li 1 , Jie Zou 1 , Karl Kratz 1 , Andreas Lendlein 1
1 , Institute of Biomaterial Science and Berlin-Brandenburg Center for Regenerative Therapies, Helmholtz-Zentrum Geesthacht, Teltow Germany
Show AbstractMesenchymal stem cells (MSCs) are capable of differentiating into multiple lineages for cell-based regenerative therapies. Recent developments in biomaterials have indicated that the physicochemical natures of materials strongly influence self-renewal, differentiation and secretome profile of MSCs [1-2]. As a complement to traditional biochemical methods, there is a great promise to use physical approach such as roughness to instruct the behavior and paracrine capacity of MSCs to optimize their therapeutic potential. Here, as a model system, both polystyrene and poly (ether imide) surfaces with three roughness levels were fabricated: R0 (smooth), R1 (with roughness level comparable to cell size) and R2 (with roughness level greater than cell size). To ensure that the cells were only in contact to the material itself, MSCs were cultured in closed polymer cups with distinct roughness on bottom surfaces, which were processed via injection molding [3]. In this study, despite a high cell viability was shown on all polymeric substrates, the apoptotic and senescent levels were highly modulated by roughness. The apoptotic level and the ratio of senescent MSCs on R1 were lower than those on smooth R0 surface. Moreover, the secretion of pro-angiogenic factors of MSCs on R1 was remarkably upregulated compared to R0 and R2 and the enhancement of those factors could be abolished via blockage of focal adhesion associated signaling pathway. In summary, the polymeric substrates with surface roughness R1 provide more superior surface environment for MSCs cultivation in respect to apoptosis, senescence and secretion. Therefore, roughness might be an important parameter to be considered for advanced biomaterial design.
References:
[1] Phillips JE, Petrie TA, Creighton FP, García AJ. Acta Biomater. 2010, 6, 12-20.
[2] Lee J, Abdeen AA, Zhang D, Kilian KA. Biomaterials. 2013, 34, 8140-8148.
[3] B. Hiebl, K. Lutzow, M. Lange, F. Jung, B. Seifert, F. Klein, T. Weigel, K. Kratz and A. Lendlein. J Biotechnol. 2010, 148, 76-82.
9:45 AM - SM8.5.02/NM10.02
Fabrication of Crosslinked Sphere Structure of Biodegradable Polymer Nanoparticles for Efficient Controlled Drug Release
Ravichandran Honnavally Kollarigowda 1 , Anu Stella Mathews 1 , Sinoj Abraham 1 , Carlo Montemagno 1
1 Chemical and Materials Engineering, University of Alberta, Edmonton, Alberta, Canada
Show AbstractPolymeric materials producing nanomaterials in the form of nanoparticles, nanorods, nanowires, nanotubes, thin films, etc. is the key element for the success of the nanotechnology, which gives extraordinary physical and chemical properties as a result of its nanosize.1-3 There have been proposals for numeral applications in the field of biomedicine, and some of them (such as sensors of DNA, the controlled release of drugs, tumor therapy, etc.) are close to achieving a successful development.4 Drug delivery systems developed through the combination of biocompatible materials and biodegradable constitute an important area of focus in the engineering of medical devices. In view of this, we Synthesized set of cross-linked sphere biodegradable polycaprolactone (PCL) nanoparticles with and without out cross linker via oil/water solvent evaporation method. PCL was synthesized by ring opening polymerization technique using metal oxide as a catalyst and alcohol as an initiator, furthermore, they are modified with a photocrosslinking agent as the end groups. The nanoparticles (Nps) were synthesized by crosslinking the hydrophobic tail by UV light irradiation and hydrophilic drug was encapsulated by sonication method with the presence of stabilizer (polyvinyl alcohol). The crosslinked nanoparticle size was monodisperse with narrow size (~100 nm) whereas solitary PCL nanoparticles were poly disperse with higher diameter (>500nm). Transmission electron microscopy (TEM) analysis revealed that these nanoparticles are assembled with hydrophobic tail structures cross-linked tail on outer sphere. The drug encapsulation efficiency controlled release is mainly influenced by the molecular weight and outer sphere content of the nanoparticles structure. The drug encapsulated crosslinked nanoparticles exhibit a pH-dependent release behavior in vitro, within 60 hours the complete drug was released in all the three pH condition pH 4, 5 and 7.4. Importantly, this novel nanoparticles system for cytotoxicity studies were carried out with cancer cell lines and it was found that these NPs system were biocompatible. Encapsulation of drug with cross-linked NPs shows comprehensive results, justifying the potential use of drugs with greater absorption cellular, sustained release, and retard the cancer cells.
Overall, these results suggest that cross-linked outer sphere biodegradable nanoparticle system are likely to have a great potential as therapeutic agents.
References.
1. K. Avgoustakis, A. Beletsi, Z. Panagi, P. Klepetsanis, A. G. Karydas and D. S. Ithakissios, J. Control. Release, 202, 79, 123–135.
2. L. Brannon-Peppas, int. J. Pharm, 1995, 116, 1-9.
3. R. H. Kollarigowda, RSC Advances, 2015, 5, 102143-102146.
4. R. CP, N. RJ, R. AJ and V. F, Nanomedicine, 2006, 2, 8-21.
10:00 AM - SM8.5.03/NM10.03
Maintenance of Neural Progenitor Cell Stemness in 3D Hydrogels Requires Matrix Remodeling
Christopher Madl 1 , Ruby Dewi 1 , Cong Dinh 1 , Kyle Lampe 1 2 , Duong Nguyen 3 , Annika Enejder 3 , Sarah Heilshorn 1
1 , Stanford University, Stanford, California, United States, 2 , University of Virginia, Charlottesville, Virginia, United States, 3 , Chalmers University of Technology, Gothenburg Sweden
Show AbstractWhile neural progenitor cells (NPCs) hold significant therapeutic promise, the difficulty and cost of expanding a large number of stem cells remains a significant barrier to widespread clinical use. Recently, 3D hydrogels have been proposed as in vitro culture platforms for the expansion of stem cell populations to overcome the space limitations of 2D culture. However, very little is known about what 3D material properties are required to maintain NPCs in an undifferentiated state for expansion. It is well-established that matrix stiffness modulates stemness in strongly adherent stem cells, including mesenchymal stem cells and muscle satellite cells, but the impact of stiffness on stemness maintenance in non-adhesion-dependent stem cells such as NPCs is not well known. Furthermore, within 3D materials, matrix degradability is another crucial design parameter that can modulate stem cell behavior, as previous studies have shown that cells cannot spread, migrate, or proliferate without first degrading their surrounding matrix. To investigate the impact of matrix stiffness and degradability on NPC stemness, we designed a family of modular, engineered elastin-like protein (ELP) hydrogels with varying stiffness (E~0.5-50 kPa) and degradability. These ELP gels consisted of structural domains derived from elastin to provide tunable stiffness and bioactive domains to permit cell adhesion and matrix degradation. Strikingly, expression of the stem markers Nestin and Sox2 by embedded NPCs was not correlated with hydrogel stiffness over the range tested. However, expression of stem markers was strongly correlated with hydrogel degradability, with increased stem maintenance in more degradable hydrogels. NPCs cultured in high degradability hydrogels exhibited increased proliferation and enhanced differentiation potential, confirming that increased degradability was associated with maintenance of a functional stem phenotype. We identified that NPCs utilize the protease ADAM9 to regulate matrix remodeling in the ELP gels. Accordingly, knockdown of ADAM9 inhibited NPC-mediated hydrogel degradation and resulted in a loss of stemness. To confirm that ADAM9-mediated remodeling is a generalizable mechanism for maintaining NPC stemness in 3D, we designed a second hydrogel system based on peptide-crosslinked poly(ethylene glycol) with independent tuning of stiffness (E~0.5-2 kPa) and ADAM9 degradability. Consistent with our findings using the ELP gels, stemness was maintained in hydrogels susceptible to degradation by ADAM9 independent of stiffness, while non-ADAM9 degradable gels resulted in a loss of NPC stemness. Our results have identified matrix remodeling as a previously unknown requirement for maintenance of NPC stemness in 3D hydrogels and suggest that ADAM9-degradable materials may be useful for expansion of therapeutically relevant numbers of undifferentiated NPCs.
10:15 AM - SM8.5.04/NM10.04
Selective Packaging of pDNA into Rod- or Toroid-Shape within Polyplex Micelles
Kensuke Osada 1 , Yanmin Li 1 , Kazunori Kataoka 2 1
1 , University of Tokyo, Tokyo Japan, 2 , Innovation Center of NanoMedicine (iCONM) , Kawasaki Japan
Show AbstractDNA undergoes large conformational transition from hydrated coil to dehydrated compact form upon polyion complexation (PIC) with polycations. The volume transition, called DNA condensation, receives remarkable attention because this is essential of the nucleosome formation and is an important part in preparation of gene delivery system. In this study, using block catiomers composed of poly(ethylene glycol) (PEG) and polycations, condensation behavior of plasmid DNA (pDNA) was investigated to accommodate a fundamental interest; how the micrometer-length pDNA changes its conformation and packaged into 100 nm-sized PIC assembly, namely polyplex micelles (PMs), within the constraint of inherent rigidity of the double-stranded DNA. Moreover, the packaged pDNA structure was attempted for control into particular ordered structures, as they are acknowledged to be relevant for eliciting biofunction of pDNA. Here, we show a success of selective packaging of pDNA into either rod-like structure or toroidal structure by modulating interactive potency between pDNA and block catiomers to form PMs, and explored potential biological activities of each structure as a gene delivery system. Interestingly, the toroid-shaped structure held intriguing biological functions; not only capable of elevating in vitro transcription efficiency but also of elevating in vivo gene transduction efficiency compared to the rod-shaped structure, which have been addressed as potent delivery system. This result demonstrated a tempting utility of the toroid structure as a novel-structured gene delivery system.
10:30 AM - *SM8.5.05/NM10.05
Metal-Organic Frameworks for Biotechnology
Paolo Falcaro 1 , Raffaele Ricco 1
1 , TuGraz, Graz Austria
Show AbstractAmong the different classes of Metal-Organic Framework (MOF) composites prepared during recent years using ceramic, metallic and polymeric nanoparticles,1,2,3,4 a new emerging type of MOF composite has been recently obtained encapsulating bio-macromolecules within MOFs.5,6,7 Thanks to different water-based synthetic approaches such as co-precipitation and biomimetic mineralization methods, different types of MOFs have been self-assembled around bio-active compounds (e.g. enzymes). These new bio-composites have shown unprecedented properties for the protection and release of proteins. This strategy enables the fast encapsulation of guests larger than micropores of MOFs. Remarkably, this novel approach overcomes the need for MOFs with pores larger than the hosted biomolecules, and enable one-pot syntheses as an alternative preparation route to post infiltration methods.8 Thus, MOFs are now considered promising materials for biotechnological applications as the encapsulation technique is inexpensive, effective and fast.6
In this presentation, an overview ranging from the exploitation of simple proteins and their constituents (amino acids)9 to complex biological systems for the formation of MOFs will be provided. The functional properties of these composites will be disclosed providing examples of other methods used for the encapsulation of proteins within MOFs, including the preparation of hollow MOF capsules.11,12 Comparison of the protective properties will be illustrated10 and the applications of proteins for the controlled localization of MOFs discussed.13 The exciting challenges and promising applications of these new MOF composites in biotechnology will be presented.
References
(1) Falcaro, Ricco, Yazdi, Imaz, Furukawa, Maspoch, Ameloot, Evans, Doonan Coord. Chem. Rev. 2016.
(2) Zhu, Xu Chem Soc Rev 2014.
(3) Doherty, Buso, Hill, Furukawa, Kitagawa, Falcaro, Acc. Chem. Res. 2014.
(4) Li, Kobayashi, Taylor, Ikeda, Kubota, Kato, Takata, Yamamoto, Toh, Matsumura, Kitagawa Nat. Mater. 2014.
(5) Lyu, Zhang, Zare, Ge, Liu, Nano Lett. 2014.
(6) Liang, Ricco, Doherty, Styles, Bell, Kirby, Mudie, Haylock, Hill, Doonan, Falcaro Nat. Commun. 2015.
(7) Shieh, Wang, Yen, Wu, Dutta, Chou, Morabito, Hu, Hsu, Wu, Tsung J. Am. Chem. Soc. 2015.
(8) Lykourinou, Chen, Wang, Meng, Hoang, Ming, Musselman, Ma J. Am. Chem. Soc. 2011.
(9) Liang, Riccò, Doherty, Styles, Falcaro CrystEngComm 2016.
(10) Liang, Coghlan, Bell, Doonan, Falcaro Chem Commun 2016.
(11) Huo, Aguilera-Sigalat, El-Hankari, Bradshaw Chem. Sci. 2014.
(12) Jeong, Ricco, Liang, Ludwig, Kim, Falcaro, Kim Chem. Mater. 2015.
(13) Liang, Carbonell, Styles, Ricco, Cui, Richardson, Maspoch, Caruso, Falcaro Adv. Mater. 2015.
11:00 AM - SM8.5/NM10
BREAK
11:30 AM - SM8.5.06/NM10.06
Mimicking Matrix Vesicles to Enhance Biomineralization of Osteoblast Cells
Fabian Itel 1 , Brigitte Stadler 1
1 , Aarhus University, Aarhus Denmark
Show AbstractLoad-bearing implants such as artificial hip or knee joints require a stable interface with bone tissue. Bioactive glass or bioactive ceramics as bulk implants or as surface coatings have so far proven to be the most successful concepts used in clinics due to their ability to induce osteoconduction or even osteostimulation. However, these ceramic and glass implants are difficult to fabricate and suffer from selective mechanical properties. Here, we aim to improve the osteoconduction of bone-forming osteoblast cells by providing a triggered mineralization at the bone tissue-implant interface. Specifically, we develop a kick-start for osteoblasts to produce extracellular matrix (ECM) and mineralization and, thus, provide a faster integration of implants within bone tissue. Our approach involves the assembly of artificial bone cells, which are composed of ECM components and matrix vesicles (MVs). Both components are important for the initial mechanism of bone mineralization. MVs are 100 nm-sized phosphatidylserine- (PS) and alkaline phosphatase (AP)-containing liposomes secreted by osteoblasts. Calcium phosphate (CaP) crystals are formed within MVs and adhere to the ECM of bone tissue, where further mineralization takes place on collagen fibrils. Our artificial bone cells are assembled in two different ways to form “soft” and “hard” microparticles using droplet-microfluidics to form agarose (hydrogel) microbeads and the layer-by-layer technique to assemble core-shell particles, respectively. Our key requirements are that the artificial bone cells i) have similar sizes to biological osteoblasts, ii) are composed of collagen fibers and iii) contain artificial MVs composed of PS-containing liposomes with encapsulated AP enzymes. AP cleaves phosphate ions from phosphomonoester substrates, which can be added to the cell media and induces CaP crystallization. Furthermore, the particle surface is crucial for cell adherence and cell interaction. Therefore, different surface coatings are employed including polydopamine, poly-L-lysine, collagen, and growth factors. The “soft” and the “hard” artificial bone cells are then compared by coculturing them with bone-forming Saos-2 cells (sarcoma osteogenic cells). The rate of mineralization is assessed by quantifying the produced mineral content and the number of cells in presence or absence of the artificial bone cells. We anticipate that our approach has the potential to enhance osteoblast-mediated bone formation.
11:45 AM - SM8.5.07/NM10.07
Micro-Fabricated Thermoresponsive Polymer-Grafted Surface for Producing Contractile Muscle Tissue Construct
Hironobu Takahashi 1 , Tatsuya Shimizu 1 , Masayuki Yamato 1 , Teruo Okano 1
1 , Tokyo Women's Medical University, Tokyo Japan
Show AbstractComplex structural organization in the body is a key factor to produce the appropriate tissue functionality. In mature skeletal muscle, for example, the muscle fibers are highly oriented to produce its mechanical functions. To engineer biomimetic tissues, therefore, a technique for mimicking microstructures in native tissues is required. Thermoresponsive poly(N-isopropylacrylamide) (PIPAAm)-grafted surface allows harvesting a cell monolayer as a single continuous cell sheet from the culture surface. Since cell sheets can be layered to produce 3D tissue construct, this cell sheet-based technology have been used effectively in the field of tissue engineering. In this study, a micro-fabricated thermoresponsive cell culture substrate was prepared to produce cell sheets composed of aligned cells. To control cell orientation in a cell sheet, stripe-shaped micro-patterns was fabricated on the thermoresponsive surface. Using this surface, we have engineered 3D muscle tissue having aligned orientation.
First, hydrophilic polyacrylamide (PAAm) was grafted spatio-selectively on a thermoresponsive surface through a photo-induced polymerization process. As a result, stripe patterns of PAAm-co-PIPAAm and PIPAAm regions (50 μm / 50 μm) was fabricated. Muscle progenitor cells, myoblasts, were aligned on the surface and reached to confluence by seeding onto the surface at 37 °C. Next, to produce a 3D tissue construct, multiple cell sheets were harvested from the surface and then layered using a gelatin gel-coated manipulator. Using this technique, multiple cell sheets were successfully layered while maintaining the cell orientation as designed. Interestingly, in the tissue construct, it was observed that aligned myoblasts changed their orientation by themselves. For example, when two cell sheets composed of aligned myoblasts were layered perpendicularly, all myoblasts of the bottom sheet re-oriented in the same direction of the top cell sheet. Using this unique behavior of myoblast, an aligned myotube construct was able to be produce by layering one aligned cell sheet and two random cell sheets. The randomly-oriented myoblasts were finally well aligned within the multilayer cell sheet construct through the self-organization process. Furthermore, the tissue construct was transferred onto a collagen gel and incubated in differentiation medium for 3 weeks. The resultant myotubes contracted by electrical pulse stimulation. Importantly, the muscle contraction was regulated directionally because of the aligned orientation of the construct.
In conclusion, we have developed a novel technique to create a muscle tissue construct through a cell sheet layering process. Uniquely, myoblasts self-organized their orientation within the tissue construct and showed regulated contraction by electrical stimulation. This structural design and functionalization could lead to truly biomimetic tissue generation, and development of in-vitro physiological tissue models.
12:00 PM - *SM8.5.08/NM10.08
Mechanobiology, Pluripotent Stem Cells, and Early Embryonic Development
Jianping Fu 1
1 , University of Michigan, Ann Arbor, Ann Arbor, Michigan, United States
Show AbstractResearch on human pluripotent stem cells (hPSCs) has significant promise for regenerative medicine, disease modeling, and developmental biology studies. In this talk, I will discuss our effort in leveraging the mechanobiology of hPSCs in conjunction with some synthetic biomimetic systems to recapitulate and model human early embryonic development. I will first discuss our effort in constructing microengineered stem cell models of early human neurological developmental processes. Specifically, we have utilized microengineered hPSC cultures to develop autonomously regionalized neuroectoderm tissues in vitro. Importantly, our findings have suggested that induction and regionalization of neuroectoderm tissues involve mechanically gated molecular signaling (including Wnt, Hippo, and BMP) through regulations of cell shape and cytoskeleton contractility to reinforce spatial patterning of cell fates in neuroectoderm tissues. Together, our data provide strong evidence supporting critical involvements of cellular mechanics and mechanobiology as control mechanisms in ensuing robust formation of regionalized neuroectoderm tissues. In the last part of my talk, I will describe an efficient method to generate early human amniotic tissue in vitro through self-organized development of hPSCs in a bioengineered niche that mimics the in vivo implantation environment. Biophysical signals from the implantation-like niche act as a switch to toggle hPSC self-renewal versus amniogenesis. Our study unveils a self-organizing nature of human amniogenesis and establishes the first hPSC-based model system for investigating peri-implantation human amnion development.
12:30 PM - SM8.5.09/NM10.09
Stabilization of Enzymes Using a Protein Matrix Identified from Squid Sucker Ring Teeth
Chelsea Riegel 1 2 , Patrick Dennis 1 , Marquise Crosby 1 , Matthew Dickerson 1 , Rajesh Naik 3
1 Materials and Manufacturing Directorate, Air Force Research Laboratory, Wright-Patterson Air Force Base, Ohio, United States, 2 , UES Inc, Dayton, Ohio, United States, 3 711 Human Performance Wing, Air Force Research Laboratory, Wright-Patterson Air Force Base, Ohio, United States
Show AbstractProtein entrapment has demonstrated great promise in the area of enzyme and biomolecule stabilization. Silk fibroin derived from the Bombyx mori silkworm, has been shown to stabilize a number of biomolecules including enzymes, vaccines and antibiotics. This is due to the highly repetitive amino acid structure of silk fibroin which lends the ability to self-assemble into ordered microcrystalline domains. The ordered structure of silk fibroin is hypothesized to create a “molecular crowding” regime where biomolecules and enzymes are stabilized through the prevention of unfolding. Based on the success of silk fibroin as a stabilizing excipient, we have looked at other potential protein matrices for their ability to stabilize labile biomolecules. The protein, suckerin-12 (S12), derived from the sucker ring teeth of the Humboldt squid, offers unique properties and potential advantages over silk fibroin, including a greatly reduced monomeric molecular weight, a more defined repeat structure and the ability to express large amounts of the protein recombinantly. Recently, S12 based hydrogels have been investigated for their shape changing properties, where under certain buffer conditions, they are induced to condense into a dehydrated state, reversibly. The potential for tunable molecular crowding led us to investigate whether S12 based hydrogels have the ability to protect labile enzymes from environmental insults. Here we present the effects of enzyme adsorption into S12 hydrogels in terms of heat stability and the ability to withstand a number of chemical insults. In this study, the ability of S12 hydrogels to protect enzymes from damage is compared to that of silk fibroin.
12:45 PM - SM8.5.10/NM10.10
Systemic Administration of Enzyme-Responsive Nanocapsules for Promoting Bone Repair
Hongzhao Qi 1 , Xiaolei Sun 2 , Xue Li 3 , Zhaoyang Li 1 , Jin Zhao 1 , Xin Hou 1 , Xubo Yuan 1 , Yunde Liu 3 , Zhenduo Cui 1 , Yunfeng Lu 4 , Xianjin Yang 1
1 Tianjin Key Laboratory of Composite and Functional Materials, School of Materials Science and Engineering, Tianjin University, Tianjin China, 2 , Department of Orthopedics, Tianjin Hospital, Tianjin China, 3 Department of Clinical Microbiology, School of Laboratory Medicine, Tianjin Medical University, Tianjin China, 4 Department of Chemical and Biomolecular Engineering, University of California, Los Angeles, California, United States
Show AbstractAccelerating the healing of fractures and bone defects by local delivery of growth factors possessing osteoinductive activity has been extensively demonstrated. Unfortunately, fractures, such as osteoporotic vertebral compression fracture, are incapable of adopting such strategy because of the difficulty of surgery or in situ injection. Systemic administration of growth factors is considered to be the appropriate solution for these diseases. But the therapy was hampered by the poor in vivo stability of growth factors, inefficient distribution in fracture site and the potential side effects such as ectopic osteogenesis. To address this challenge, we here conceived a growth factor systemic delivery platform based on nanocapsules possessing bone fracture-targeting ability and enzyme-responsive releasing ability, taking the advantages of the unique physiological character of bone fracture, i.e., the rupture and leakage of blood vessels and the over-expression of matrix metalloproteinases (MMP). Bone morphogenetic protein-2 (BMP-2), 2-(methacryloyloxy)ethyl phosphorylcholine (MPC) and MMP-degradable peptide were chosen as the model growth factor, monomer and crosslinker, respectively. Electrostatic and hydrogen bonding interactions enriched the monomers and crosslinkers around BMP-2 molecules and in situ free radical polymerization formed a thin polymer layer around BMP-2s, forming the nanocapsules with controlled composition. These nanocapsules are of uniform small size (~30 nm) possessing long circulation time (half-life is ~40 h) and can be passively targeted to fracture site through the ruptured and leaked blood vessels after systemic administration. Once accumulated in fracture site, the shells of nanocapsules could be degraded by MMP and thus BMP-2s were released. Animal experiments prove BMP-2 nanocapsules show better bone repair ability than native BMP-2. Furthermore, owe to the improvement of biodistribution of BMP-2 and the enzyme-responsive releasing characteristic, systemic administration of BMP-2 nanocapsules didn’t cause obvious ectopic osteogenesis. The results of this study demonstrate nanocapsules can enhance the in vivo stability and fracture sites delivery efficiency of growth factors and avoid their ectopic osteogenesis potential, realizing the repair of bone fracture by systemic administration of growth factors.
SM8.6: Bioinspired Materials
Session Chairs
Wednesday PM, April 19, 2017
PCC North, 100 Level, Room 124 A
2:30 PM - SM8.6.01
Effect of Drug-Polymer Interaction on Mechanical and Release Behavior of Drug-Eluting Fibers
Shih-Feng Chou 1 2 , Kim Woodrow 2
1 Mechanical Engineering, University of Texas at Tyler, Tyler, Texas, United States, 2 Bioengineering, University of Washington, Seattle, Washington, United States
Show AbstractElectrospun drug-eluting fibers have demonstrated advantages in loading efficiency and ability to tune release profiles compared to other therapeutic carriers used for implantable medical devices. In such instance, the mechanical performance of fibers may be significantly affected by the high drug loading. However the effect of drug loading on the mechanical integrity and release behavior of the delivery system has not been fully investigated but is integral for function. Here, we measure bulk mechanical properties of blend fibers made from polycaprolactone (PCL) and poly(D,L-lactic-co-glycolic) acid (PLGA) at various weight ratios and combined with up to 40 wt% of a small molecule water-soluble drug (tenofovir, TFV) to inform drug-polymer interactions at the molecular level. Dogbone specimens were prepared by punching the electrospun fiber mats from a stainless steel die for tensile testing on an Instron. Young’s moduli were used for the development of a Voigt model to estimate drug partition in the blend fibers. HPLC analysis was used to quantify drug concentration in the release media for up to 10 days.
Uniaxial tensile tests performed on electrospun fibers made with various PCL/PLGA ratios and drug loadings revealed drug-polymer interactions. Average Young’s moduli and tensile strength of blank PCL/PLGA fibers gradually increased with increasing PLGA contents in the blend fibers. However, TFV loaded fibers suggested a different trend of mechanical properties from blank fibers, indicating the effect of drug-polymer interactions. In addition, increasing drug loading to 40 wt% decreased the mechanical properties of PCL/PLGA 20:80 fibers due to a strong plasticizing effect from the drug, and consequently led to a burst release at higher drug loading. Results on fiber mechanical properties suggested a strong drug-polymer interaction, which mediates drug release rates. Dogbone samples collected from the release media at predetermined time points showed significant decreases in average Young’s modulus and tensile strength as compared to the blank fibers. The additional loss in mechanical properties was associated with drug release behaviors. Our results showed the dependence of fiber mechanical properties on drug release rates and biodegradation as a result of drug loading. Interestingly, TFV release rates increased in pre-stretched fibers. Mechanical assessment on drug partition in PCL/PLGA fibers suggested a higher drug content in the PCL phase than in the PLGA phase. This study contributes significantly to the understanding of drug-polymer interactions in electrospun drug-eluting fibers and provides important property information for implantable therapeutic carriers in future clinical applications.
2:45 PM - SM8.6.02
pH-Responsive, Lysine-Based, Hyperbranched Polymers Mimicking Cell-Penetrating Peptides for Efficient Intracellular Delivery
Shiqi Wang 1 , Rongjun Chen 1
1 , Imperial College London, London United Kingdom
Show AbstractThe insufficient delivery of biomacromolecular therapeutic agents into the cytoplasm of mammalian cells remains a major barrier to their pharmaceutical applications. Cell-penetrating peptides (CPPs) are considered as potential carriers for intracellular delivery of macromolecular drugs. However, due to the positive charge of most CPPs, strong non-specific cell membrane bindings may lead to relatively high toxicity. Herein, we report a series of anionic, cell-penetrating peptide-mimicking, lysine-based hyperbranched polymers, which were membrane-lytic at late endosomal pH while inactive at physiological pH. The polymers with different branching degrees were prepared by a facile one-pot synthetic strategy. To our knowledge, it is the first report of anionic, hyperbranched, CPP-mimicking polymers. The pH-responsive conformational alterations and the multivalency effect of the hyperbranched structures were demonstrated to effectively facilitate the interactions between the polymers and cell membranes, thus leading to significantly enhanced membrane-lytic activity compared with linear ones. The unique structures and pH-responsive cell-penetrating abilities make these polymers promising candidates for intracellular delivery and endosome release of biomacromolecular payloads.
3:00 PM - SM8.6.03
Fluorescent Molecular Force Probe that Operates in Soft Materials
Shohei Saito 1 , Hiroshi Yabu 2
1 , Kyoto University, Kyoto Japan, 2 , Tohoku University, Sendai Japan
Show AbstractForce mapping at molecular scale is an important technology in rheology and mechanobiology. Flexible and aromatic photoresponsive (FLAP) system has been developed as fluorescent molecular force probe, which shows force-responsive conformational change with fluorescence color conversion in a real-time and reversible manner. The FLAP molecules are useful for visualizing the stress concentration in polymer films and understanding the force transduction in biological systems.
Here we report the preparation of the FLAP-doped luminescent elastomer film that shows the reversible response to the mechanical stress, in which the flexible FLAP fluorophore is stretched to exhibit a different emission color. The unique dynamic fluorophore with single-component RGB luminescent properties has been synthesized based on the molecular design of rigid-flexible hybridization. In general, the conformational flexibility is key to switching fluorescence properties, while some planar, rigid structures are favorable for producing strong luminescent properties. To combine the advantages of flexibility and rigidity, we have designed and synthesized a hybrid pi system that consists of a flexible cyclooctatetraene (COT) core and anthraceneimide wings [1-3]. This hybrid pi system exhibits a conformation-dependent emission from a single component fluorophore. That is to say, the pi system gives rise to a blue emission from the V-shaped structure doped in a elastomer film, while a green emission was observed from the planar geometry which should be produced in the stretched elastomers. This result demonstrates that the FLAP molecule actually works as fluorescent force probe even in the condensed materials [4].
[1] S. Saito* et al., J. Am. Chem. Soc. 2013, 135, 8842−8845 (Highlighted in C&EN).
[2] S. Saito* et al., Chem. Eur. J. 2014, 20, 2193–2200 (Inside Cover).
[3] S. Saito* et al., Nature Commun. 2016, 7, 12094.
[4] S. Saito* and H. Yabu* et al., to be submitted.
3:15 PM - SM8.6.04
Rapid Electro-Formation of Robust and Transparent Biopolymer Gels in Prescribed 3D Shapes
Ankit Gargava 1 , Srinivasa Raghavan 1
1 , University of Maryland College Park, College Park, Maryland, United States
Show AbstractGels of biopolymers such as alginate are routinely used to encapsulate biological cells and proteins for applications in drug delivery and tissue engineering. These gels are created by combining sodium alginate with a source of divalent ions like Ca2+. Recently, researchers have demonstrated the ability to deposit alginate gels using electric fields. For example, these gels can be deposited at the anode of an electrochemical cell where the local pH is considerably more acidic than in the bulk solution. However, these processes are limited to generating 2-D films of alginate, and the need for strong pH gradients hampers the inclusion of pH-sensitive species within the films. Here, we present an alternative approach for rapidly forming 3-D alginate gels upon application of an electric field. In this approach, a molded 3-D gel of gelatin with dissolved CaCl2 is placed in a beaker containing a sodium alginate solution. These are connected to a DC power source, and when a voltage is applied, an alginate/Ca2+ gel is formed around the gelatin in a shape that is the inverse replica of the original mold. The alginate gels are transparent and robust, and the process is mild and compatible with pH-sensitive materials. Gels in several 3-D architectures can be formed by this method that cannot be achieved through conventional methods.
4:30 PM - SM8.6.05
Self-Assembly of Repeat Polypeptides
Isaac Weitzhandler 1 , Ingo Hoffmann 2 , Sylvain Prevost 3 , Jonathan McDaniel 4 , Michael Dzuricky 1 , Michael Gradzielski 5 , Ashutosh Chilkoti 1
1 Biomedical Engineering, Duke University, Durham, North Carolina, United States, 2 , Institut Laue Langevin, Grenoble France, 3 , European Synchrotron Radiation Facility, Grenoble France, 4 Chemical Engineering, University of Texas at Austin, Austin, Texas, United States, 5 Physical Chemisry, Technische Universitat Berlin, Berlin Germany
Show AbstractIn recent decades, block copolymers have been studied extensively. When the blocks have different solubilities, block copolymers can self-assemble into a range of structures including micelles, vesicles, lamellae, and liquid crystals. In recent years, recombinant DNA techniques have allowed for the development of repeat polypeptides such as elastin-like, resilin-like, and silk-like polypeptides. One considerable advantage of recombinant block copolypeptides is that because they are synthesized by a host organism from a specific DNA template, they are perfectly sequence-defined and monodisperse.
For synthetic block copolymers, the relationship between hydrophilic weight fraction, polymer hydrophobicity, charge, and self-assembly has been characterized theoretically, computationally, and experimentally. In the case of recombinant block copolypeptides however, despite the number of different sequences and self-assembled structures reported, there exists only a limited understanding of the relationship between polypeptide sequence and self-assembled morphology. The present work aims to address this shortcoming of the literature through the synthesis and characterization of systematically designed families of recombinant repeat block copolypeptides, thus revealing the “rules” governing their self-assembly.
The first set of repeat block copolypeptides consists of a high molecular weight, hydrophilic elastin-like polypeptide fused to a short hydrophobic block consisting of aromatic amino acids and glycine spacers. Despite their high hydrophilic weight fraction (in excess of 90%), these block copolypeptides self-assemble into cylindrical micelles, rather than the expected star-like morphology.
The second set of repeat block copolypeptides are resilin-like/elastin-like block copolypeptides wherein the molecular weight of the hydrophobic resilin-like block and the hydrophilicity of the hydrophilic elastin-like block are varied systematically. The self-assembly of these block copolypeptides obeys a number of simple rules from polymer physics relating to the hydrophobic weight fraction, the hydrophilicity of the corona-forming block, the morphology of the self-assembled micelles, and the polypeptide chain conformations.
The bulk phase, liquid crystalline self-assembly of repeat polypeptides was also characterized. Repeat polypeptides form highly ordered liquid crystalline phases such as hexagonally oriented cylinders and lamellae. The feature sizes are responsive to molecular weight and temperature. Upon the phase transition of one block, block copolypeptides exhibit both order-order and order-disorder transitions. These highly ordered bulk phases can be deposited on surfaces to form highly regular, biologically patterned surfaces, which enable many biomedical applications.
4:45 PM - SM8.6.06
Artificially Engineered Protein Polymer Materials for Selective Biomolecular Separation
Minkyu Kim 1 2 3 , Bradley Olsen 3
1 Department of Materials Science and Engineering, The University of Arizona, Tucson, Arizona, United States, 2 Department of Biomedical Engineering, The University of Arizona, Tucson, Arizona, United States, 3 Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show AbstractUnderstanding the function of biological systems can provide inspiration to develop new functional materials, such as mussel byssus mimicking adhesives, muscle-inspired energy dissipative materials, and thermo-responsive elastin-based drug delivery vehicles. One of the interesting studied biological functions is the selective filtration through pores on the nuclear membrane. Traditional separation membranes nonspecifically filter small particles by decreasing membrane mesh sizes, which also reduces filtering rates. Alternatively, the nuclear membrane pores specifically filter only a small group of selected molecules, independent of size, at a very high rate between the cell cytoplasm and the nucleus while rejecting the passage of undesired molecules into the nucleus. The pore is filled with the gel network, composed of nucleoporins, proteins containing Phe-Gly (FG) repeat sequences that contribute to specific binding to nuclear transport receptors (NTRs). The selectivity of target molecules is achieved via complexation with NTRs that facilitate transport of the targets into the nucleoporin gel network. This fast, specific selectivity of biological filters, unprecedented in synthetic polymer membrane filters, makes them of interest scientifically as materials with a potential for broad impact in advanced separation technologies.
Inspired by the selective filtration by the nuclear membrane, a biopolymer system that can separate target biomolecules using a facilitated diffusion-based mechanism has been developed. The system includes two components: engineered NTRs fused with a peptide tag that can "catch" target biomolecules and a recently developed nucleoporin-like protein (NLP) polymer hydrogel that can selectively "trap" target molecule-NTR complexes via a similar selective filtering mechanism as the biological membrane. The NLP hydrogel is shown to effectively capture target molecule-NTR complexes present at single nanomolar concentrations in the environment. An 11-fold enrichment of target molecules to unselected environmental biomolecules is observed in the NLP gel compared to control gels, which do not contain FG repeats in the protein polymer network. We found that the high selectivity requires both moderate interactions between the hydrogel and the target-NTR complex as well as high gel concentration to reduce the hydrogel pore size. As a proof of concept of "catch-and-trap", a partial green fluorescent protein sequence and staphylococcal enterotoxin B toxoid, related to toxic shock syndrome, are both separated from biomolecule mixtures using NLP hydrogels and engineered NTRs that contain binding tags for the corresponding target molecules. This represents a versatile system for fusing NTRs with diverse peptide tags and enabling the selective binding and separation of a wide variety of biomolecules, such as high value antibodies and biological toxins, for biomedical, food toxicology and defense applications.
5:00 PM - *SM8.6.07
Protein-Engineered, Self-Assembling Bio-Inks for Cell-Based 3D Printing
Sarah Heilshorn 1
1 , Stanford University, Stanford, California, United States
Show AbstractDespite the rise of 3D printing of thermoplastics both in industry and the general public, a key limitation preventing the widespread use of cell-based 3D printing is the lack of suitable bio-inks that are cell-compatible and have the required properties for printing. Current commonly used biomaterials have distinct limitations when used as a bio-ink including difficulty maintaining a homogeneous cell suspension, avoiding cell damage during extrusion, customizing the printed matrix properties to facilitate cell-matrix interactions, and printing within a bath to prevent cell dehydration while preserving high print resolution. We have designed a new family of tunable biomaterials specifically designed for cell-based 3D printing. These hydrogel-based bio-inks are produced from blends of engineered recombinant proteins and peptide-modified, naturally occurring biopolymers such as alginate and hyaluronic acid. These materials undergo two-stages of crosslinking: (i) weak, peptide-based, self-assembly to homogeneously encapsulate cells in a shear-thinning hydrogel within the ink cartridge and (ii) stimuli-responsive crosslinking post-printing to rapidly stabilize the construct. Benefits of this two-stage crosslinking strategy include the prevention of cell sedimentation within the ink cartridge, mechanical shielding of the cell membrane from damaging extrusion forces during printing, rapid post-print self-assembly within an aqueous bath that prevents cell dehydration, and fine-tuning of the printed scaffold mechanical properties for optimal cell-matrix interactions.
5:30 PM - SM8.6.08
Materials Construction through Peptide Design and Solution Assembly into 1D or 2D Physical Polymers
Darrin Pochan 1
1 , University of Delaware, Newark, Delaware, United States
Show AbstractSelf-assembly of molecules is an attractive materials construction strategy due to its simplicity in application. By considering peptidic molecules in the bottom-up materials self-assembly design process, one can take advantage of inherently biomolecular attributes; intramolecular folding events, secondary structure, and electrostatic interactions; in addition to more traditional self-assembling molecular attributes such as amphiphilicty, to define hierarchical material structure and consequent properties. These self-assembled materials range from hydrogels for biomaterials to nanostructures with defined morphology and chemistry display for inorganic materials templating. The local nano- and overall network structure, and resultant viscoelastic and cell-level biological properties, of hydrogels that are formed via beta-hairpin self-assembly will be presented. Importantly, the hydrogels do not form until individual peptide molecules intramolecularly fold into a beta-hairpin conformation in response to specific solution stimuli. Subsequently, specific, intermolecular assembly occurs into a branched nanofibrillar network. These peptide hydrogels are potentially excellent scaffolds for tissue repair and regeneration due to inherent cytocompatibility, porous morphology, and shear-thinning but instant recovery viscoelastic properties. Slight design variations of the peptide sequence allow for tunability of the self-assembly/hydrogelation kinetics as well as the tunability of the local peptide nanostructure and hierarchical network structure. In turn, by controlling hydrogel self-assembly kinetics, one dictates the ultimate stiffness of the resultant network and the kinetics through which gelation occurs. During assembly and gelation, desired components can be encapsulated within the hydrogel network such as drug compounds and/or living cells to make composite systems. The system can shear thin but immediately reheal to preshear stiffness on the cessation of the shear stress. By using the shear-thinning, rehealing behavior, one can perform multiple injections to produce layered hydrogels, channels of hydrogel in a hydrogel matrix and domains of one hydrogel within another matrix. These composite constructs are critical for the mimicking of in vivo, multi-cell environments in the cerebellum in order to study the fundamental biology and disease states of the brain. Additionally, a new system comprised of coiled coil motifs designed theoretically to assemble into two-dimensional nanostructures not observed in nature will be introduced. The molecules and nanostructures are not natural sequences and provide opportunity for arbitrary nanostructure creation with peptides.
SM8.7: Poster Session II: Advanced Polymers
Session Chairs
LaShanda Korley
Muhammad Yasar Razzaq
Thursday AM, April 20, 2017
Sheraton, Third Level, Phoenix Ballroom
9:00 PM - SM8.7.01
Laser Writing Assembly of Block Copolymer on Chemically Modified Graphene
Hyeong Min Jin 1 2 , Joonwon Lim 1 2 , Kyung Eun Lee 1 2 , Sang Ouk Kim 1 2
1 , KAIST, Daegeon Korea (the Republic of), 2 , National Creative Research Initiative Center for Multi-Dimensional Directed Nanoscale Assembly, Daejeon Korea (the Republic of)
Show AbstractPolymer self-assembly commonly suffers from retarded equilibrium structure formation arising from the large diffusion barrier of long chain molecules. We introduce low energy laser photothermal treatment to effectively promote the polymer self-assembly and achieve highly aligned 10-nm-scale patterned structures on arbitrary substrates. Weak intensity Infrared or visible laser beam is directly radiated at block copolymer thin films in an ambient condition for area-selective ultrafast self-assembly within several seconds. In-plane scanning of the laser beam induces directional self-assembly of laterally ordered vertical lamellar or cylinder nanodomains from quasi static order/disorder boundary. Solution processing of chemically modified graphene film is employed as flexible and conformal light absorbing layer to facilitate the laser writing self-assembly on transparent, nonplanar, and mechanically flexible surface geometry.
9:00 PM - SM8.7.02
Amyloid Structures Produced from Recombinant Gas Vesicle Proteins
Joseph Tang 1 2 , Claretta Sullivan 1 , Joseph Slocik 1 2 , Patrick Dennis 1 , Wendy Goodson 1
1 , Air Force Research Laboratory, Wright-Patterson AFB, Ohio, United States, 2 , UES, Inc., Dayton, Ohio, United States
Show AbstractBacterial micro-compartments (BMCs) are structures that perform unique biological functions in microorganisms. A notable trait of BMCs is their selective permeability to certain chemical species. For example, the carboxysome is permeable to HCO3–, but not CO2 and O2. Bacterial gas vesicles (GVs) are intracellular structures that play a role in the regulation of cellular buoyancy in response to light intensity. Like the BMCs, these structures consist of a protein shell that is permeable to various gas molecules, but not water or ions. Genes encoding GV associated proteins from cyanobacteria and halobacteria have been identified, but the biochemical and biophysical properties of these proteins as well as their ability to self-assemble into functional structures are not yet fully understood. In an effort to employ GVs for biomaterials and bioengineering applications, we have developed a methodology for the production and purification of recombinant GV components. Under the proper conditions, these components self-assemble into amyloid-like structures that demonstrate buoyant behavior in aqueous solution. The characterization of these amyloid-like structures is presented here.
9:00 PM - SM8.7.03
Study of Protein-Carbohydrate Covalent Linkage in Gelling Arabinoxlyans
Mayra Mendez-Encinas 1 , Elizabeth Carvajal-Millan 1 , Ciria Figueroa-Soto 1 , Elisa Valenzuela-Soto 1 , Madhav Yadav 2 , Agustin Rascon Chu 1 , Yolanda Lopez-Franco 1 , Jaime Lizardi-Mendoza 1 , Alberto Nunez 2
1 , CIAD, Hermosillo, Sonora, Mexico, 2 , USDA, Wyndmoor, Pennsylvania, United States
Show AbstractArabinoxylans (AX) are polysaccharides from cereal grains. AX can form gels through covalent cross-linking of ferulic acid. The properties of AX gels depend on the structural characteristics such as protein content. The objective of the present study was to investigate the nature of protein-carbohydrate covalent linkage in gelling AX. The protein associated to AX was studied by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and showed a molecular weight range from 6 up to 14 kDa. The matrix-assisted laser desorption/ionization with automated tandem time-of-flight mass spectrometry of the protein produced an amino acid partial sequence: alanine, threonine, tryptophan, glutamic acid, glycine, glutamic acid and arginine. The most abundant amino acids in protein were histidine, aspartic acid and threonine. The protein fraction attached to AX was removed using the enzyme O-glycosidase, suggesting an O-glycosidic covalent linkage between AX and the protein through serine and/or threonine.
9:00 PM - SM8.7.04
Polymer–Industrial Waste Fly Ash Cenosphere (FAC) Composite Film for Electromagnetic Interference Shielding
Pritom Bora 1 , K Vinoy 1 , . Kishore 1 , Praveen Ramamurthy 1
1 , Indian Institute of Science, Bangalore India
Show AbstractFly ash cenosphere (FAC), an industrial waste product rich in alumina (Al2O3) and silica (SiO2) (typically hollow microsphere), with an average size ~ 50 µm was cleaned by acid-base treatment followed by vacuum drying. The NiO is coated over FAC through chemical heterogeneous precipitation and thermal reduction (at 700 oC) method. The coating thickness was observed to be ~ 800 nm under optimal conditions. The oxidative polymerization of aniline on NiO-FAC composites were carried out under nitrogen at -30±2 oC and PANI-NiO-FAC composite was synthesized. Thus, obtained PANI-NiO-FAC composites were solution processed using DMPU followed by acid vapour treatment and also used as filler in weather resistive polyvinylbutyral (PVB) to get free standing flexible films. The surface morphology of the prepared films were studied along with elemental mapping. The electromagnetic interference shielding effectiveness (EMI SE) of as prepared composite films were investigated in J-band (5.8-8.2 GHz), X-band (8.2-12.4 GHz) and Ku-band (12.4-18 GHz) by using a vector network analyzer (complete two port thru-reflect-line calibration was performed in all the frequency bands before measurements). The most effective average EMI SE ~ 23 dB (20 dB EMI SE corresponds to 99 % shielding) was observed for PANI-NiO-FAC composite film (81±2 µm) whereas PANI-FAC composite film (80±2 µm) shows ~ 17 dB EMI SE. The optimally prepared flexible PVB-PANI-NiO-FAC composite film (279±2 µm) shows ~ 22 dB average EMI SE, comparatively higher EMI SE than PVB-PANI-FAC composite film (285±2 µm, ~17 dB). The EMI shielding due to absorption (SEA) was found to be intrinsically dominant for each composite film. Further, enhancement of microwave conductivity, total dielectric loss, EM attenuation constant with frequency indicates excellent EMI SE (SEA) of these composite films. These films can be coated over any substrate and a potential candidate to protect against EMI for modern communication devices, unmanned vehicles, robotics as well as microwave engineering.
9:00 PM - SM8.7.05
Syneresis in Arabinoxylan Gels—Rheology and Microstructure
Ana Maria Morales-Burgos 1 , Elizabeth Carvajal-Millan 1 , Norberto Sotelo-Cruz 2 , Agustin Rascon Chu 1 , Yolanda Lopez-Franco 1 , Jaime Lizardi-Mendoza 1
1 , CIAD, Hermosillo Mexico, 2 , Universidad de Sonora, Hermosillo Mexico
Show AbstractArabinoxylans (AX) gels have been studied as delivery matrices and could have potential applications for colon-specific drug delivery due to their porous structure, stability under changes in pH and temperature as well as their specific degradation by colonic microbiota. AX gels have been described as gels that present no syneresis, however, in the current investigation a maize bran AX containing a high amount of ferulic acid (7 µg/mg AX) presented this phenomenon. The kinetics of gelation of AX solutions at 1% and 2% (w/v) was rheologically monitored by small amplitude oscillatory shear following the storage (G’) and loss (G”) modulus over time. Maximum G’ values were 655 Pa and 889 Pa for AX at 1% and 2% (w/v), respectively. Covalent cross-linking structures (dimers and trimers of ferulic acid) content in AX gels at 1 and 2 % (w/v) increased after syneresis. The syneresis ratio (% Rs) of gels describes the amount of solvent released from the gel network. In the present work increasing AX concentration decreases % Rs value from 80 to 70 as result of the corresponding G’ increase. Scanning electron microscopy images of AX gels showed that after syneresis the microstructure of the gel was more compact and still heterogeneous. Syneresis effect was assumed to be result of the polymer network contraction by a slow further crosslinking of the chains due to further oxidation of ferulic acid.
9:00 PM - SM8.7.06
Molecular Identity and Viscoelastic Properties of Gelling Arabinoxylans Isolated by a Semi-Pilot Scale Procedure
Jose Fierro-Islas 1 , Elizabeth Carvajal-Millan 1 , Rafael Canett-Romero 2 , Agustin Rascon Chu 1 , Marcel Martinez-Porchas 1 , Jorge Marquez-Escalante 1 , Alma Campa-Mada 1
1 , CIAD, Hermosillo Mexico, 2 , Universidad de Sonora, Hermosillo Mexico
Show AbstractArabinoxylans (AX) are polysaccharides of cereal grains. Maize is the main source for bioethanol production in some countries. The dry milling of maize produces several co-products and bran represents the major fraction, which usually ends up in the distillers dried grain with solubles (DDGS). The development of high added-value products from DDGS has increased and could be used as a source for the potential extraction of AX. This polysaccharide is constituted of a linear backbone of xylose to which arabinose substituents are attached. Some of the arabinose residues are ester linked to ferulic acid. The presence of ferulic acid gives AX the ability to form covalent gels. In recent years, the interest in AX and AX gels has increased since several studies have reported that this biomaterial present prebiotic, antioxidant, antitumoral and immunomodulatory activity. In addition, AX gels could have potential applications on microencapsulation of macromolecules. The objective of this research was to extract AX from DDGS at a semi-pilot scale and determine their molecular identity and viscoelastic properties. The yield of AX was 4.2 % (w/w dry basis). Extracted AX were analyzed by Fourier Transform Infra-Red Spectroscopy (FT-IR) and small amplitude oscillatory shear. The spectral FT-IR pattern in region of 1200-850 cm-1 was characteristic of AX. The maximum absorption band (1035 cm-1) was assigned to C-OH bending and the signals at 1070 and 898 cm-1 were related to the antisymmetric C-O-C stretching mode of the glycosidic link and β(1-4) linkages between the sugar units. Gels at 2% in AX (w/v) presented an elasticity (G’) value of 77 Pa.
9:00 PM - SM8.7.07
Photocrosslinking of Methacrylated Pectin—pH Stability and Gelling Capability
Yaeel Cornejo-Ramirez 1 , Elizabeth Carvajal-Millan 1 , Francisco Brown-Bojorquez 2 , Alison Dominguez-Chavez 1 , Agustin Rascon Chu 1
1 CTAOV, Centro de Investigacion en Alimentacion, Hermosillo, Sonora, Mexico, 2 Polimeros, Universidad de Sonora, Hermosillo, Sonora, Mexico
Show AbstractThe pharmaceutical industry uses controlled release matrices for drug delivery in the human body. An important factor in oral administration is the pH stability of such matrices. Pectins have long been used as excipient for its suitable properties; however, pH sensibility of pectin gels is a major drawback for controlled delivery matrices. In this regard, the aim of this research was to determine the effect of methacrylic anhydride addition to low methoxy citrus pectin, on its physicochemical properties and gelling ability by photocrosslinking. First, the citrus pectin was chemically modified; 1% (w/v) pectin in phosphate buffer (pH 7) was mixed with methacrylic anhydride at 1:1, 1:2 and 1:3 proportions. The derivatization at 1:2 (pectin solution: methacrylic anhydride) ratio showed peaks by FT-IR at 949 cm-1, 1737 cm-1 and 1616 cm-1 wave number, which suggest the presence of the vinylidene group, the C=O and C=C bond, respectively in the structure of pectin. The HPLC chromatogram showed that the neutral sugars profile was not affected. Photocrosslinking was done for a 3% (w/v) pectin solution with 10% (v/v) 2-Hydroxy-4′-(2-hydroxyethoxy)-2-methylpropiophenone solution as a photoinitiator at 265 nm during 5 min. The modified pectin gel presented a strength of 0.022±0.003N/ mm; 1.55 times lower than unmodified citrus pectin ionic hydrogels. Interestingly, the photocrosslinked hydrogel was stable at acidic and basic pH, but not at neutral pH. Photocrosslinked hydrogel have enough firmness to remain intact through the digestive tract conditions; in theory, the gels could be disintegrated by pH in the colon. Further research is required to fully assess the potential of photocrosslinked pectin hydrogels for design of controlled/ target delivery matrices.
9:00 PM - SM8.7.08
Sugary Interfaces Mitigate Contact Damage Where Stiff Meets Soft
Sangchul Rho 1 , Hee Young Yoo 1 , Sangsik Kim 1 , Dong Soo Hwang 1
1 , POSTECH, Pohang Korea (the Republic of)
Show AbstractThe byssal threads of the fan shell Atrina pectinata are non-living functional materials intimately associated with living tissue, which provide an intriguing paradigm of bionic interface for robust load-bearing device. An interfacial load-bearing protein (A. pectinata foot protein-1, apfp-1) with L-3,4-dihydroxyphenylalanine (DOPA)-containing and mannosebinding domains has been characterized from Atrina’s foot. apfp-1 was localized at the interface between stiff byssus and the soft tissue by immunochemical staining and confocal Raman imaging, implying that apfp-1 is an interfacial linker between the byssus and soft tissue, that is, the DOPA-containing domain interacts with itself and other byssal proteins via Fe3+–DOPA complexes, and the mannose-binding domain interacts with the soft tissue and cell membranes. Both DOPA- and sugar mediated bindings are reversible and robust under wet conditions. This work shows the combination of DOPA and sugar chemistry at asymmetric interfaces is unprecedented and highly relevant to bionic interface design for tissue engineering and bionic devices.
9:00 PM - SM8.7.10
Functionalization of Carbon Particles by Atom Transfer Radical Polymerization
Nurettin Sahiner 1 , Sultan B Sengel 1
1 , Canakkale Onsekiz Mart Univ, Canakkale Turkey
Show AbstractSpherical carbon particles (CPs) with controllable sizes and surfaces were prepared hydrothermal treatment using sucrose as precursor. The CP preparation was accomplished in two steps; firstly, dewatering of sucrose at low temperatures, and secondly carbonization at high temperatures. The micro/nano sized CPs were functionalized by N-isopropylacrylamide (NIPAM), 2-Acrylamido-2-methylpropane sulfonic acid (AMPS), (3-Acrylamidopropyl)-trimethylammonium chloride (APTMACI) to have the corresponding polymers on CPs. The monomers were grafted onto the CPs’ surface via atom transfer radical polymerization (ATRP). The grafting process was accomplished by oxidation of CPs to -OH groups, and then attaching macro initiator on the surfaces.
The size of polymers that were grown from the surface of CPs can be controlled by feed ratio of the used monomers. CPs with various functional group polymers on the surfaces were functionalized and characterized via FT-IR, NMR, SEM, TEM and TG analysis. Moreover, copolymerization of these monomer with different hydrophobic monomer to induce additional properties will be discussed. The responsive behaviors of CP-p(NIPAM), CP-p(AMPS) and CP-(APTMACl) composite in various solutions against environmental stimuli such as temperature, pH and ionic strength were investigated. These novel CPs-based micro/nanomaterials with tailoring structure, architecture, and properties are promising candidates for various biomedical, energy and environmental applications.
9:00 PM - SM8.7.11
Microgels Derived from Different Forms of Carrageenans, Kappa, Iota, and Lambda for Biomedical Applications
Nurettin Sahiner 1 , Selin Sagbas 1 , Selehattin Yilmaz 1
1 , Canakkale Onsekiz Mart University, Canakkale Turkey
Show AbstractPoly(Carrageenan) microgels were synthesized by three main types of carrageenan such as kappa (κ), iota (ι), and lambda (λ) by using divinyl sulfone or epoxy group containing crosslinkers via microemulsion technique. These natural based κ-, ι-, and λ-carrageenan microgels were chemically modified by various cationic and anionic agents such as 3-chloro2-hydroxy propyl ammonium chloride (3-CHPACl), diethylenetriamine (DETA), and Taurine (TA). Optical microscope, scanning electron microscope (SEM), dynamic light scattering (DLS), zeta potential measurements and FT-IR spectroscopy were used for the characterization of the particles. Antimicrobial properties of the poly(Carrageenan) microgels were determined against common bacteria such as against gram negative Escherichia coli ATCC 8739 and Pseudomonas aeruginosa ATCC 10145, and gram positive Staphylococcus aureus ATCC 6538 and Bacillus subtilis ATCC 6633 bacteria strains. Blood compatibility of the microgels was determined by protein adsorption, hemolysis and blood clotting tests. Furthermore, the microgels and their modified forms were also investigated for potential drug delivery vehicles in physiological conditions at pH 7.4, 37.5 oC.
9:00 PM - SM8.7.12
Copper-Chitosan Transparent Antimicrobial Coatings
Debirupa Mitra 1 , En-Tang Kang 1 , Ramanathan Kollengode 1 , Matthew Cove 1 , Koon Gee Neoh 1
1 , NUS, Singapore Singapore
Show AbstractHealth-care associated infections (HCAIs) cause considerable mortality and morbidity, and inanimate environmental surfaces in hospitals can act as pathogen reservoirs wherein pathogens are inadvertently transferred to patients via hands or gloves of healthcare workers. In our project, we seek to develop antimicrobial surface coatings which can reduce bacterial burden on hospital inanimate objects such as equipment panels and touchscreens. Our focus is on chitosan derivatives since chitosan is an inexpensive, nontoxic and a naturally derived polysaccharide which is known to possess broad antimicrobial activity. The quaternization of chitosan greatly increases its solubility in water as well as its antimicrobial efficacy. Quaternized chitosan (QCS) prepared with acrylate groups can be readily grafted on polymer films under UV irradiation to give highly stable, non-cytotoxic QCS coatings. These coatings can kill about 90% of bacterial cells, when placed in contact with contaminated droplets for 2 h. To further increase the bacterial killing efficacy, copper was introduced onto the QCS-grafted films via palladium-free electroless deposition process. The positively charged quaternary ammonium groups of QCS promote deposition of copper on the surface without any catalytic pre-treatment. The copper content of these modified films was determined to be ~ 4 µg/cm2 and both Cu(0) and Cu(II) states of copper were present on the surface. These coatings can reduce bacterial count by 95% and 100%, when placed in contact with contaminated droplets for 1 h and 1.5 h respectively. Additionally, the copper-containing films were found to have no significant cytotoxic effects on fibroblast cells placed in contact with these films. Thus, these transparent copper-containing films with high antibacterial efficacy can potentially be used over high-touch areas in hospitals to prevent pathogen transmission.
9:00 PM - SM8.7.13
Poly(lactic acid)/Cellulose Nanofibril/Epoxidized Soybean Oil Ternary System towards Tougher and Stiffer Nanocomposites
Xiangtao Meng 1 , Halil Tekinalp 1 , Soydan Ozcan 1
1 Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States
Show AbstractPoly(lactic acid) (PLA) as a promising renewable and biodegradable thermoplastic polymer has received tremendous attentions in applications such as medical devices, packaging, and additive manufacturing. The broader application potentials, however, have been restricted largely by the inherent brittleness of PLA. While most of previous approaches, such as the use of plasticizers, were able to increase the ductility, the stiffness and strength of the composites were usually sacrificed. In the current study, cellulose nanofibril (CNF) as nanofiller and epoxidized soybean oil (ESO) as coupling agent were utilized in the PLA-CNF-ESO ternary composite system. Mechanical performances of the composites including stiffness, ductility, and toughness were significantly improved, comparing with those of pristine PLA, CNF-PLA, and ESO-PLA systems. For example, the ternary composites are 10-fold tougher than pristine PLA or PLA composites enhanced only with CNF. In the meantime, Young’s moduli and tensile strengths of the ternary composites are 20-44 % and 8-58 % higher than those of PLA-ESO binary composites. Interfacial interactions in CNF-ESO, CNF-PLA, and ESO-PLA interfaces were investigated by thermal analysis, spectroscopic and microscopic approaches. Possible mechanisms on how the ternary system enhances mechanical performances will also be discussed.
9:00 PM - SM8.7.14
Ratiometric Fluorescent Microspheres for Sensing Oxygen
Gang Li 1 , LanFeng Liang 2 , Chengzhu Liao 1 , Jiapei Jiang 1 , Yanqing Tian 1
1 Department of Materials Science and Engineering, Southern University of Science and Technology, Shenzhen, Guangdong, China, 2 , Southern University of Science and Technology, Shenzhen, Guangdong, China
Show AbstractPolymer microspheres have received much attention because of their superior thermal and solvent resistance, mechanical strength, surface activity and adsorption properties. In our research, monodisperse polystyrene microspheres with controlled diameters ranging from 600 nm to 2 mm have been prepared through dispersion polymerization. In order to maintain a narrow particle size distribution and achieve the controllable particle diameters, we adopted two-stage polymerization proposed by Mitchell A. Winnik[1]. We extended our research for mono-dispersed polystyrene-based oxygen sensors and expected the porous and well aligned structures of the microspheres can achieve high sensitivity and stability by adjusting oxygen permeability. For sensing oxygen accurately in complicated biological environment, our microsphere-based sensors were designed as ratiometric fluorescent sensors[2] in which an platinum octaethylporphyrin (PtOEP) fluorophore as an oxygen probe and rhodamibe B (Rhod) derivative fluorophore as an oxygen-insensitive internal reference were enwrapped. We called the modified microspheres “PR-PSMs” for short. Through the two-stage polymerization, core-shell structures were prepared with the properties of mono-dispersity and smooth surface. Under an excitation at 540 nm, two emission peaks at 580 nm and 650 nm were observed, indicating that Rhod and PtOEP fluorophores were successfully embedded in the polystyrene particles. These PR-PSMs showed stable dispersion in water, which is most likely due to the positive charges of the Rhod derivative. The oxygen probe PtOEP in microspheres showed excellent sensitivity to oxygen. Moreover, PR-PSMs exhibited stronger fluorescence emission and better photo-stability than those of PtOEP in THF. The PR-PSMs powder was used to test the oxygen concentration of the obturator because the ratios of fluorescence intensity and O2 concentration could be described by a perfect linear regression relationship when the O2 concentration changed. Furthermore, the intensity could keep on 90% after repeating the gas concentration test for 10 times. What's more, the fluorescence intensity of the PR-PSMs solution at different pH and temperature values could keep on a higher level. In the end, we applied the PR-PSMs in escherichia coli and studied the property and the cytotoxicity. The result of the oxygen concentration changed coincided with that obtained in obturator test. In addition, the viability of coli was basically not affected after coli cells were incubated with indicated concentrations of oxygen sensors for 2 h. In this work, PR-PSMs were prepared with excellent O2-dependent performance which could be applied to environmental protection and biological healthy test.
References:
[1] Song,J.S.;Tronc,F.;Winnik,M.A. J.Am.Chem.Soc., 2004, 126, 6562-6563.
[2] Hongguang Lu, Yuguang Jin, Yanqing Tian, Weiwen Zhang, Mark R. Holl, Deirdre R. Meldrum, J. Mater. Chem., 2011, 21, 19293-19301.
9:00 PM - SM8.7.15
Microstructured Substrates Modulate Interleukin-6 Secretion in Human Mesenchymal Stem Cells
Xun Xu 1 , Weiwei Wang 1 , Karl Kratz 1 , Nan Ma 1 , Andreas Lendlein 1
1 , Institute of Biomaterial Science and Berlin-Brandenburg Center for Regenerative Therapies, Helmholtz-Zentrum Geesthacht, Teltow Germany
Show AbstractThe therapeutic potential of mesenchymal stem cells (MSCs) has been well demonstrated in various clinical applications, in which their functional benefits have been mainly attributed to the secretion of soluble factors [1-2]. The enhancement of the therapeutic potential of MSCs by physical and chemical property from cell culture substrate is a safe and effective modulation strategy since they are highly sensitive to their microenvironment such as the elasticity and surface topography [3-5]. In this study, we demonstrated that the geometry of polymeric substrate regulated the interleukin-6 secretion of human adipose derived MSCs. Polystyrene substrates comprising arrays of square-shaped (S50) or round-shaped (R50) microwells (side length or diameter of 50 µm and depth of 10 µm) were developed by injection molding [6]. Cell shape of MSCs was strongly modulated by the geometric cues on the microstructured substrates. MSCs seeded on S50 microwells displayed stronger F-actin stress fiber when compared to R50. Notably, the upregulated secretion of interleukin-6 and the strong enhancement of nuclear transcription factors STAT3 were detected in MSCs seeded on S50 substrate. The geometry-dependent modulatory effects were highly associated with ROCK signaling pathway. The inhibition of ROCK signaling cascade abolished the differences in interleukin-6 secretion. These findings highlight the possibility to control the functions of stem cells via microstructures in combination with the manipulation of ROCK signaling pathway.
References:
[1] Madrigal M, Rao KS, Riordan NH. J Transl Med. 2014,12, 260.
[2] Kyurkchiev D, Bochev I, Ivanova-Todorova E, Mourdjeva M, Oreshkova T, Belemezova K, Kyurkchiev S. World J Stem Cells. 2014, 6, 552-570.
[3] Engler AJ, Sen S, Sweeney HL, Discher DE. Cell. 2006, 126, 677-689.
[4] Xu X, Wang W, Kratz K, Fang L, Li Z, Kurtz A, Ma N, Lendlein A. Adv Healthc Mater. 2014, 12,1991-2003.
[5] Abagnale G, Steger M, Nguyen VH, Hersch N, Sechi A, Joussen S, Denecke B, Merkel R, Hoffmann B, Dreser A, Schnakenberg U, Gillner A, Wagner W. Biomaterials. 2015, 61, 316-326.
[6] B. Hiebl, K. Lutzow, M. Lange, F. Jung, B. Seifert, F. Klein, T. Weigel, K. Kratz and A. Lendlein. J Biotechnol. 2010, 148, 76-82.
9:00 PM - SM8.7.16
Synthetic Routes for Metal-Bearing Hydrophobic Graphite Sponges
Andrew Patalano 1 , Fabian Villalobos 1 , Mihri Ozkan 1 , Cengiz Ozkan 1
1 , University of California, Riverside, Riverside, California, United States
Show AbstractMetal-bearing mesoporous graphite sponges have been synthesized from low-cost, sustainable starting materials for use in applications including environmental cleanup, antibacterial sorbents and sensors. Sol-gel polymerization in aqueous acidic conditions combined Mx(NO3)x precursors (M=Li, Na, Al, K, Fe, Co, Ni, Cu, Ag), carbohydrates (d-glucose, lactose, sucrose) and polyvinyl alcohol into gel networks which were then cured and reduced at high temperature with H2 gas leaving metal particles embedded in the graphite network. These networks showed absorptive properties of oleophilicity and superhydrophobicity (152° contact angle with water). These sponge structures were characterized with Raman spectroscopy, FTIR, BET, XRD, SEM and TEM, and their absorbent properties were qualitatively investigated with a variety of different non-polar solvents.
9:00 PM - SM8.7.17
Self-Folding Behavior of Smart Biopolymers in Detection of Aromatic Alcohol
Amrita Rath 1 , Santhosh Mathesan 1 , Raghunandan Pratoori 1 , Pijush Ghosh 1
1 , Indian Institute of Technology Madras, Chennai India
Show AbstractStimuli responsive biopolymers respond to changes in the humidity, pH, temperature and solvent by undergoing a significant change in their structure and property. Self-folding is one of the means to respond to these external stimuli, applying which desired patterns and shapes necessary for certain functionality can be achieved. Chitosan, one of the promising biopolymers, shows the reversible folding behavior in response to water due to differential swelling along the thickness. This folding behavior can be exploited and suitably engineered to detect the presence of a biological molecule, measure pH of a solvent, identify the functional groups of desired interest etc. In this work, we show the possibility of detecting aromatic alcohol (Resorcinol) concentration applying self-folding behavior of chitosan thin film. The folding behavior is characterized in terms of time, rate and extent of folding. The interaction of water molecules with the amine and hydroxyl reactive groups of chitosan determines the diffusion characteristics of water which leads to self-folding. Self-folding due to water diffusion is again dependent on its mechanical properties. However, low mechanical properties of film at the hydrated state affect its folding behavior. Therefore, an attempt is made to improve its mechanical properties by adding cross-linking agent. A control and predictable pathway of folding and unfolding is achieved by this modification. The modified film is further applied for detecting the aromatic alcohol concentration having a reactive OH group which can interact with reactive groups of chitosan. An initial study shows a significant difference in the total time, rate and extent of folding for different concentration of aromatic alcohol solution. The mechanics and mechanism of folding and unfolding in the presence of aromatic alcohol molecules is one of the major objectives of this work. Detecting this particular chemical group has two broad areas of application. One is in detection of industrial waste water and groundwater containing phenolic compounds. The other application is in detecting the presence of a biological molecule having benzene ring and hydroxyl as a reactive group from folding characteristics. Also, appropriate calibration of the folding can lead to a suitable sensor design.
9:00 PM - SM8.7.18
Planar Phase Separation of Weak Polyelectrolyte Brushes in Poor Solvent
Kai Gao 1 , Logan Kearney 1 , John Howarter 1
1 , Purdue University, West Lafayette, Indiana, United States
Show AbstractPoly(acrylic acid) (PAA) brushes were synthesized on silicon wafer substrates using a silane linker and Z-group RAFT method, which enables the controlled variation of brush characteristics. Atomic force microscopy (AFM) was used to characterize the brush morphology in dry state, which ranged from isolated globules to micelles to a continuous film featuring dimples. Surface morphology was primarily determined by total grafted polymer concentration with a critical polymer concentration between 4.5 and 6.5 × 10-23mol/nm2, where the polymer rich regions transition from micellar islands to a continuous film with dimples. However, even at the highest grafting densities and brush strand lengths used in this study, a flat homogenous film was not formed. Morphological consequences of the solvent and thermal history were shown to persist into the dry state. X-ray photoelectron spectroscopy (XPS) was used to quantify the degree of remaining salt after drying. It was found that a higher relative amount of salt was retained after drying in the lower grafting density samples.
Symposium Organizers
Andreas Lendlein, Helmholtz-Zentrum Geesthacht
Kevin Cavicchi, University of Akron
LaShanda Korley, Case Western Reserve University
Bernd Rehm, Massey University
Symposium Support
MedShape, Inc.
MilliporeSigma
SM8.8: Advanced Functional Materials I
Session Chairs
Thursday AM, April 20, 2017
PCC North, 100 Level, Room 124 A
9:45 AM - SM8.8.01
Structure and Dopant Engineering in PEDOT Thin Films—Dramatic Conductivity Enhancement and Application to Thermoelectric Devices
Jean-Pierre Simonato 1 , Alexandre Carella 1 , Magatte Gueye 2 , Renaud Demadrille 2 , Jerome Faure-Vincent 2 , Etienne Yvenou 1
1 LITEN, CEA, Grenoble France, 2 INAC, CEA, Grenoble France
Show AbstractPoly(3,4-ethylenedioxythiophene) (PEDOT) is certainly the most known and most used conductive polymer because it is commercially available and shows great potential for organic electronic, photovoltaic, and thermoelectric applications. Studies dedicated to PEDOT films have led to high conductivity enhancements. However, an exhaustive understanding of the mechanisms governing such enhancement is still lacking, hindered by the semicrystalline nature of the material itself. In this communication, we report the development of highly conductive PEDOT films by controlling the crystallization of the PEDOT chains and by a subsequent dopant engineering approach using iron(III) trifluoromethanesulfonate as oxidant, N-methyl pyrrolidone as polymerization rate controller and sulfuric acid as dopant. XRD, HRTEM, Synchrotron GIWAXS analyses and conductivity measurements down to 3 K allowed us to unravel the organization, doping, and transport mechanism of these highly conductive PEDOT materials. N-methyl pyrrolidone promotes bigger crystallites and structure enhancement during polymerization, whereas sulfuric acid treatment allows the replacement of triflate anions by hydrogenosulfate and increases the charge carrier concentration. We finally propose a charge transport model that fully corroborates our experimental observations. These polymers exhibit conductivities up to 5400 S cm−1, it is to our knowledge the highest value reported so far for PEDOT thin films. Since high power factor can be achieved, this materials show great promise for room temperature thermoelectric applications. First thermoelectric devices using this polymer will be presented.
References: Chem. Mater., 2016, 28, 3462−3468; Chem. Sci., 2015, 6, 412-417; J. Mater. Chem. C, 2014, 2, 1278-1283.
10:00 AM - *SM8.8.03
Chemical Shaping: Synthesizing Complex Polymeric Nano and Microstructures
Stefan Seeger 1 , Georg Artus 1 , Sandro Olveira 1
1 , University of Zurich, Zurich Switzerland
Show AbstractThe synthesis of nano and microstructures are an emerging field in chemistry and materials science. They can be made from a large variety of materials, for example metals, semi-metals, or polymeric substances. Usually, these particles exhibit a comparable simple shape. However, in some cases more complex structures, for example spirals and stars have been described. Beside carbon, silicone is an interesting material for nanoparticle. Some years ago we have presented the synthesis of silicone nano filaments in particular for surface coatings. Recently, we have shown a mechanism, explaining how these one dimensional growth can be explained. Based on this synthesis scheme we are able to synthesize silicone nanoparticles of different shapes depending on the reaction conditions. Some of these structures exhibit a shape complexity which goes far beyond wires and filaments. The mechanism of this synthesis is applicable not only to silicone structures but also to other chemical compounds, for example germanium oxide. In this presentation we will give an overview about the synthesis came and present reaction conditions allowing the directed growth of of nano and microstructures of complex shape. References: G. R. J. Artus, S. Jung, J. Zimmermann, H. P. Gautschi, K. Marquardt, S. Seeger, Adv. Mater. 2006, 18, 2758; Stojanovic, S. Olveira, M. Fischer, S. Seeger, Chem. Mater. 2013, 25, 2787; G Artus, S Olveira, D Patra, S Seeger, Macromol. Rapid Comm. 2017, 38, 1600558
10:30 AM - SM8.8.05
Membranes with Functional Nanopores from the Assembly of Random Copolymer Micelles
Ayse Asatekin 1
1 , Tufts University, Medford, Massachusetts, United States
Show AbstractRegulating permeation through materials is crucial for many applications including selective membranes, controlled drug delivery, and packaging. An ideal membrane material would pass the desired molecules with little resistance (high permeability) while preventing the passage of all else (high selectivity). However, synthetic materials today cannot meet this challenge. There are no commercially available membranes that can separate small molecules of similar size in the liquid phase based on their chemical properties. In contrast, biological pores in cell membranes regulate the transport of a huge array of molecules and ions into and out of cells with exceptional specificity and permeability to their target compound. In this study, we aim to prepare synthetic polymer membranes that mimic two key features of these biological systems: Constricted pores only 1-5 nm in diameter, lined with functional groups lining the pore that interact with the target during passage. The nanostructure constricts flow and confines all components passing through, forcing them to interact with the chemically functional walls. As an initial system, we focus on membranes capable of charge-based separation through electrostatic interactions. To build these nanostructured layers using scalable techniques, we deposited packed arrays of polymer micelles whose coronas exhibit carboxylic acid groups onto a porous support membrane. Random copolymers that combine highly hydrophobic fluorinated repeat units of trifluoroethyl methacrylate (TFEMA) with ionizable repeat units of methacrylic acid (MAA) form micelles and vesicles in methanol. The micelle size can be tuned between 8-35 nm by the addition of various salts. This is, to our knowledge, the only report on the formation of micelles from a random/statistical copolymer in an organic solvent. When these micelles are coated onto the surface of a porous support membrane whose pores are smaller than the micelles and then immersed into water, a selective layer of micelles packed together is formed. The gaps between the micelles act as nanochannels functionalized with carboxylic acid groups. The membrane showed charge-based selectivity between organic dye molecules, efficiently rejecting negatively charged solutes while allowing the passage of neutral solutes. Two-dye separation tests showed a negatively charged dye being retained by >85% whereas a positively charged dye with a similar molecular charge was retained by <30%. Furthermore, the carboxyl groups can be post-functionalized to alter the selectivity of the membrane for desired separations. This demonstrates the potential of using polymer self-assembly and functionality to design membranes that mimic biological pores while maintaining scalable manufacturing methods. We believe these approaches will eventually lead to novel membranes that can separate molecules of similar size but different chemical structure.
11:15 AM - SM8.8.06
Synthesis and Characterization of Zwitterionic Polymer Brush Functionalized Hydrogels
Allen Osaheni 1 , Ivan Gitsov 2 , Patrick Mather 3 , Michelle Blum 1
1 Mechanical and Aerospace Engineering, Syracuse University, Syracuse, New York, United States, 2 Chemistry, New York State College of Environmental Science and Forestry, Syracuse, New York, United States, 3 Chemical Engineering, Bucknell University, Lewisburg, New York, United States
Show AbstractFreeze-thaw poly (vinyl alcohol) hydrogels (PVA-H) offer great potential for a number of biomedical applications due to their biomimetic mechanical properties and biocompatibility. Despite this, use of PVA-H for load bearing applications has been limited due to poor performance in boundary lubrication compared to natural tissue such as articular cartilage. Recently, zwitterionic polymer brushes have been shown to act as effective boundary lubricants on rigid substrates; however, to the best of our knowledge, the synergistic effects of zwitterionic brushes coupled with the biomimetic fluid load support exhibited by hydrogels has not been reported. We report here on our investigation involving synthesis and characterization of two unique types of polymer brush functionalized PVA hydrogels whose surface chemistry has been verified via ATR-FTIR. The zwitterionic polymers of choice include poly([2-(methacryloyloxy) ethyl] dimethyl-(3-sulfopropyl) ammonium hydroxide) (PMEDSAH) and poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC). Preliminary results from tribological characterization reveals as much as a 63% reversible change in coefficient of friction in response to an ionic stimulus. We report further on surface energy characterization of the biomimetic gels via contact angle goniometry using water and 1,2-dichloroethane as test fluids and through AFM experiments. Finally, the impact of brush functionalization on the mechanics of the tribologically enhanced gels will be reported with comparison to natural articular cartilage within the context of Hertzian biphasic theory.
11:30 AM - SM8.8.07
Incorporation of Glucose in Triblock Copolymers to Create Sustainable Adhesive and Elastomeric Materials
Mohammadreza Nasiri 1 , Theresa Reineke 1
1 , University of Minnesota, Minneapolis, Minnesota, United States
Show AbstractThermoplastic elastomers (TPEs) are of high utility and interest for a wide variety of applications, ranging from adhesives and electronics to clothing and automotive parts. With the ability to fine-tune the chemical TPE architecture and properties, triblock copolymers with an ABA architecture can be designed to comprise of a soft/rubbery middle segment (B) with two hard/glassy blocks at the ends (A). Self-assembly of the glassy endblocks into microstructures at ambient temperatures results in physical cross-links between the A segments, with the rubbery blocks bridging between the hard domains. The physically cross-linked network creates a superior resistance to flow, resulting in a material with elastomeric properties, and also allows for preparation of processable and recyclable materials. Here, we have directly functionalized glucose, as a sustainable component derived from an abundant and inexpensive feedstock, to create glucose-6-acrylate-1,2,3,4-tetraacetate (GATA). Poly(GATA) imparts a glassy segment into the block copolymers and was copolymerized with rubbery n-butyl acrylate (n-BA) via Reversible Addition-Fragmentation Chain Transfer (RAFT) polymerization, to create PGATA-b-PnBA-b-PGATA triblock copolymers. The triblock copolymers exhibited excellent thermomechanical characteristics, with decomposition temperatures higher than 279 degrees Celsius. Moreover, phase-separation and formation of physically cross-linked networks was confirmed by small-angle X-ray scattering (SAXS) for the synthesized triblock copolymers. Pressure sensitive adhesives formulated from these copolymers exhibited adhesion properties comparable or superior to the commercial products. As one example, a 102 kDa triblock copolymer, containing 12 wt% GATA, showed peel adhesion of 5.07 N.cm -1, when combined with 40 wt% of a rosin ester tackifier. The mechanical behavior of the polymers was investigated by tensile experiments and moderate elastomeric properties were observed. For instance, a 126 kDa triblock copolymer, containing 29 wt% GATA, fails at 650 kPa stress and 400% elongation. This work presents a new family of glucose-based ABA-type copolymers that demonstrate functionality of a glucose-based feedstock for developing green and practical polymeric materials.
11:45 AM - SM8.8.08
Modulating the Size and Mechanical Properties of Squid Protein Hydrogels with Anions
Patrick Dennis 1 , Marquise Crosby 1 , Maneesh Gupta 1 2 , Joseph Slocik 1 2 , Rajesh Naik 1
1 Materials and Manufacturing Directorate, Air Force Research Laboratories, Dayton, Ohio, United States, 2 , UES, Dayton, Ohio, United States
Show AbstractThe squid sucker ring teeth (SRT) assembly is a sclerotized, proteinaceous structure used for grappling and predation. Recently, it was found that the SRT assembly is made up of a family of proteins named suckerins. The suckerins hold promise to rival silk proteins in terms of mechanical strength while doing so at a significantly lower monomeric molecular weights. Here we demonstrate the generation of enzymatically-crosslinked suckerin hydrogels using a low molecular weight suckerin family member, suckerin-12. Upon exposure of the suckerin-12 hydrogels with salts, a significant decrease in hydrogel size occurs where bulk water is driven out and a condensation of the protein hydrogel occurs. Interestingly, the contraction rate as well as the mechanical properties of the condensed hydrogels are greatly dependent on the type of anion present in the salt. The differences observed in the mechanical properties of suckerin-12 hydrogels do not seem to be explained by changes in secondary structure or an increase in crystallinity, but correlate with the presence or absence of microstructures as measured by SEM. Finally, the final size of contracted suckerin-12 hydrogels is dependent on both the initial concentration of the hydrogels as well as the anion used for condensation. Together, the results indicate that by spatially-controlling casting density and the exposure to anions, features can be created in suckerin-12 hydrogels with tunable mechanical properties.
12:00 PM - SM8.8.09
Bio-Derived Polymers for Sustainable Lithium-Ion Batteries
Tyler Schon 1 , Andrew Tilley 1 , Colin Bridges 1 , Mark Miltenburg 1 , Dwight Seferos 1
1 , The University of Toronto, Toronto, Ontario, Canada
Show AbstractThe increased use of portable electronics, electric vehicles, and the emergence of the Internet of Things requires energy storage that is inexpensive, sustainable, and able to accommodate a wide range of form factors. Unlike the metal-based electrodes widely used in current energy storage technologies, biologically-derived organic polymers are able to address these issues due to their high abundance, renewable feedstocks, flexibility, and ease of processing. We recently reported the first bio-derived pendant polymer cathode for lithium-ion batteries that uses a redox-active moiety derived from riboflavin (vitamin B2) to store charge. A semi-synthetic methodology is used to prepare the pendant polymer, composed of a poly(norbornene) backbone and pendant flavin units, which reduces the number of chemical transformations required to form this new functional material. Lithium-ion batteries incorporating this polymer have a 125 mAh g-1 capacity and a 2.5 V operating potential using lithium as the anode. We find that charge transport is greatly improved by forming hierarchical structures of the polymer with carbon black, and we provide new insight into electrode degradation mechanisms that can be used to design high performance battery materials. The development of the bio-derived polymer and its application in a lithium-ion battery will be discussed.
12:15 PM - SM8.8.10
Hierarchical Ion Effects in Tuning Mechanical Properties of Marine Biopolymers
Maneesh Gupta 1 , Patrick Dennis 1 , Kellie Becknell 1 , Marquise Crosby 1 , Rajesh Naik 1
1 , Air Force Research Laboratory, Dayton, Ohio, United States
Show AbstractThe lightweight construction, robust mechanical properties, and novel hardening mechanisms of invertebrate biting and piercing structures highlights their potential as models for advanced polymer systems. The mechanical properties of these structures often surpass those of synthetic polymers and can be comparable to mineralized composite tissues found in higher organisms. In stark contrast to mineralized tissues, however, the composition of sclerotized tissues is predominantly organic with most consisting of highly ordered carbohydrate, protein, and polyphenolic compounds. Significant progress has been made toward understanding the structure property relationships for several materials, including some jaws and mandibles. In particular, prior work has demonstrated the role of coordinated zinc metal ions on the hardness and stiffness of the jaw structures in the marine worm Nereis virens.
In this work, we demonstrate the ability to express and purify gram scale quantities of the protein NVJP-1 (identified as the primary protein in Nereis virens jaw structures) and to process the purified protein into macro-scale cross-linked hydrogels. These cross-linked gels were utilized to study the role of transition metal cations on the mechanical properties of NVJP-1. It was found that a hierarchical sequence of ion treatments is required for modulating the mechanical properties of the hydrogels. First, a primary anion was found to be responsible for contraction of the hydrogels, which was a necessary priming step for Zn induced hardening. Next, the Zn metal cation was able to bind to the NVJP-1 protein acting as coordinate cross-links and resulting in dramatic increase (>100 fold) in elastic modulus. Finally, we found that the acetate anion could be replaced to modulate the interaction of Zn with the protein’s histidine groups further modulating the stiffness and viscoelastic properties of the material. The ability to dramatically tailor the mechanical properties of polymers through the incorporation of and ionic “dopant” allows for the potential to create structures and materials with graded and reconfigurable mechanical properties.
12:30 PM - *SM8.8.11
Rheology of Living Bioinks Used in 3D Printing
Patrick Ruehs 1 , Manuel Schaffner 1 , Fergal Coulter 1 2 , Samuel Kilcher 3 , Andre Studart 1
1 Complex Materials, Department of Materials, ETH Zürich, Zurich Switzerland, 2 School of Mechanical & Materials Engineering, University College Dublin, Dublin Ireland, 3 Laboratory of Food Microbiology, Department of Health, Science and Technology, ETH Zürich, Zurich Switzerland
Show AbstractDespite recent advances in 3D printing of cell-loaded scaffolds for biomedical applications, specific cell localization into complex 3D geometries without a loss of printing accuracy remains a major challenge. Here we report on a 3D printing platform that, besides freeform shaping, enables the digital fabrication of cell-laden hydrogels with full control over the spatial distribution and concentration of cells in complex 3D architectures.
For 3D printing we use a recently developed multimaterial direct ink writing technique (1) which allows us to incorporate various types of cells in biocompatible inks within the same 3D printed material. Our bioinks are designed by combining different hydrogels to form a paste-like ink, which after printing is crosslinked by low intensity UV light. To obtain accurate 3D printed structures, we determine the ideal rheological properties prior, during and after printing, demonstrating the effect of the printing steps on the bioink. In a pre-characterization step, we study the viscosity and viscoelastic properties of our bioinks, revealing shear thinning that is ideal for extrusion based printing, and viscoelasticity for structure retention in 3D printing. With alternating shear rate and oscillation cycles, we mimic the printing process and determine the bioink viscous and elastic recovery after deposition on the substrate. With this approach we are able to obtain a hydrogel which supports cell growth while still maintaining a high shape fidelity in 3D printing.
As a proof of concept, highlighting the importance of rheology in 3D printing, we demonstrate that cell proliferation is a function of viscosity and oxygen availability. By fine-tuning the single ink components, we adjust the viscosity to match the growth profile of our cells. With this versatile printing platform we envision the use of additive manufacturing materials combined together with cells to be used for new and biomedical applications.
(1) Kokkinis, D., Schaffner, M. & Studart, A. R. Multimaterial magnetically assisted 3D printing of composite materials. Nat Commun 6, (2015).
SM8.9: Shape-Memory and Shape-Changing Polymers
Session Chairs
Karl Kratz
Muhammad Yasar Razzaq
Thursday PM, April 20, 2017
PCC North, 100 Level, Room 124 A
2:45 PM - SM8.9.01
Thermally-Induced Reversible Bidirectional Shape-Memory Effect of Hybrid Nanocomposites
Muhammad Yasar Razzaq 1 , Marc Behl 1 , Andreas Lendlein 1
1 , Helmholtz-Zentrum Geesthacht, Teltow Germany
Show AbstractMagnetic shape-memory polymer composites (mSMPc) containing magnetite nanoparticles (MNP) as filler, have great potential for in vivo applications, as MNP act as contrast agent and are useful for magnetic resonance imaging (MRI).[1] These composites have been realized with one-way and reversible shape-memory effect (rSME) under stress-controlled conditions.[2] However, an important issue in the preparation of such composites is the suppression of nanoparticles aggregation and segregation from the polymer matrix.
Here, we report on the reversible bidirectional shape-memory effect (rbSME) of the hybrid nanocomposites (H-NC) based on oligo(ω-pentadecalactone) (OPDL) and covalently integrated MNP (Ø = 10±1 nm) acting as netpoints. The covalent integration of the MNP enabled a uniform dispersion of the MNP and increased the elastic modulus of the composites.[2] The rbSME, which is the capability of the polymers to perform reversible movements under stress-free conditions has been demonstrated in polymer networks with two crystallizable switching domains or in polymers providing a single broad melting transition.[3,4] Here, the crystals with a high melting temperature (Tm) acted as geometry determining domain (GD), while the crystals with lower Tm acted as actuating domains (AD). We designed H-NCs, in which the OPDL crystalline domains would play the role as AD and GD. By increasing the MNP content in H-NCs from 5 to 11 wt%, the Tm,OPDL was increased from 73 °C to 80 °C, attributed to the larger sized crystals.[2] The rbSME of the H-NCs was demonstrated by a one-step programming procedure, which consisted of elongation to εmax = 50% at Thigh (Thigh > Tm,OPDL), and fixation at Tlow (Tlow < Tm,OPDL). The rbSME was observed by heating the sample to Tsep, resulting in a partial melting of the OPDL crystalline domains acting as AD and subsequent cooling of the sample to Tlow under stress-free conditions. The cyclic change in temperature between Tsep and Tlow resulted a directed crystallization and melting of the AD, enabling the rbSME under stress-free conditions. The effect was quantified by examining the reversible strain (εrev) and fixation efficiency (Qef) of the composites. A restraining effect of the MNP netpoints on the chain mobility, which resulted in a decreased εrev with increasing MNP content, was observed. The value of εrev was decreased from 8.2±0.2% for H-NC5 with 5 wt% MNP to 3.2±0.3% for H-NC11 with 11 wt% of MNP. The two-way actuation of these H-NCs has a tremendous potential for designing smart devices applied as artificial muscles, sensors or in robotics.
References
[1] Q. Zhao, H. J. Qi, T. Xie, Prog. Poly. Sci. 2015, 50, 79.
[2] M. Y. Razzaq, M. Behl, K. Kratz, A. Lendlein, Adv. Mater., 2013, 25, 5730.
[3] M. Behl, K. Kratz, J. Zotzmann, U. Nochel, A. Lendlein, Adv. Mater. 2013, 25, 4466.
[4] M. Behl, K. Kratz , U. Nöchel, T. Sauter, A. Lendlein, Proc. Natl. Acad. Sci. USA. 2013, 110,1255.
3:00 PM - SM8.9.02
Photopolymerizable and Robust Liquid Crystal Elastomers
Nicholas Godman 1 , Anesia Auguste 1 , Timothy White 1
1 , Air Force Research Laboratory, Wright-Patterson AFB, Ohio, United States
Show AbstractLiquid crystal elastomers (LCE) are loosely crosslinked polymer networks that exhibit exceptionally large and potentially useful responses associated with their anisotropy. Recent reports detail the ability to locally orient the director profile within LCEs, thereby “programming” the material and opening up new potential applications, i.e. actuators, dampeners, or sensors. Here, we will detail our efforts in making and improving on facile chemistries that are conducive to the photoalignment methods employed to program the orientation of LCEs. Specifically, we employ a so called “click” reaction between thiols and alkenes to prepare programmable LCEs. A major advantage of the thiol-ene reaction is the ease at which it can proceed: either via radical addition to olefins or through anionic addition to α,β-unsaturated carbonyl compounds. Herein, we explore new thiol-ene chemistry formulations targeted at generating more robust LCEs by systematically varying the monomers and investigating the substituent effects on the mechanical properties of the materials. The solventless, photochemical methods employed here allows for easy, facile film generation, and improvements to the LCEs strength, toughness, and elasticity will be discussed.
3:15 PM - *SM8.9.03
Micromachined Shape Memory Polymers Actuators for Flexible Haptic Displays
Herbert Shea 1
1 , EPFL, Neuchatel Switzerland
Show AbstractWe report on a fully-latching flexible haptic display with 768 individually addressable taxels based on an array of micromachined Shape Memory Polymers (SMP). Fabricating the dense array of mechanical actuators required for large-area dynamic graphical displays for visually-impaired users is challenging due to the simultaneous large force and large displacements requirements on each taxel (the mechanical analog of a pixel), coupled with the need for a very high fill factor. To be easily explored using our sense of fine touch, each taxel must move by at least 0.5 mm with a holding force of over 250 mN. Making a flexible haptic display is even more challenging, as the use of soft materials reduces the force that can be generated by the actuator.
We exploit the reversible thousand-fold change in the stiffness of shape memory polymers (SMP) when heated above its glass transition temperature to lock in the position of each taxel. The core of our haptic displays consists of a 60 µm thick SMP membrane (glass transition temperature of 65°C) on which a matrix of addressable and stretchable 3 mm diameter, 15 µm thick, microheater heaters patterned. The SMP membrane is bonded on top of a 3D-printed flexible holder with fluidic channels to apply a single controlled air pressure to all taxels. Electrical interconnection for row/column addressing is accomplished using a flex PCB. The user touches a flexible 3D-printed pin interface with 768 plastic pins, placed on the SMP membrane.
For each refresh cycle, the taxels that we wish to displace are electrically heated to 80°C, a positive or negative pressure is applied, and the Joule heating current is then removed to lock in the position. The pixels that are not heated simply do not move (as they are below the glass transition temperature). We achieve 5 s refresh time for a 24x32 display with 4 mm pitch, 400 mN holding force and 650 μm displacement per taxel. The patterns are easily felt by sighted and blind users alike.
We will discuss application of this latching SMP approach to other fields including fluidics and adaptive optics.
3:45 PM - SM8.9.05
Extrusion of UV-Responsive Thermoplastic Liquid Crystal Elastomers
Laura Beckett 1 , Richard Trask 2 , Annela Seddon 1 , George Whittell 1 , Ian Manners 1
1 , University of Bristol, Bristol United Kingdom, 2 , University of Bath, Bath United Kingdom
Show AbstractLiquid crystal elastomers (LCEs) are polymeric materials capable of shape change when the application of an external stimulus triggers a phase transition from an ordered liquid crystalline (LC) mesophase to a disordered isotropic phase, resulting in a reversible contraction. Their potential for use as soft actuators, however, is limited by the need to generate and fix an aligned LC monodomain, and this typically is achieved by introducing covalent crosslinks that prevent further processing of the material. Thermoplastic LCEs are therefore desirable as it should be possible to align the LC component by the shear forces encountered during processing, and for this order to be locked-in on cooling from the isotropic melt. An extruded stimuli-responsive ‘filament’ could then be processed into a more useful form, for example by fused filament fabrication (FFF) 3D printing, increasing the design space for these materials.
In this work a synthetic route to a previously reported thermoplastic LCE [1] has been developed which improves on originally reported yields to yield a sufficient quantity for processing by extrusion. The triblock copolymer backbone phase separates to crosslink the LCE, whilst the side-chain azobenzene-containing mesogen imparts UV-responsive behaviour. The influence of bonding type and spacer length between the mesogen and polymer backbone on the physical and thermal properties of the polymer, specifically the glass transition and isotropic temperatures, has been investigated, as well as rheological measurements to compare melt viscosity at various temperatures with that of standard 3D printing materials. This has afforded materials with improved characteristics with respect to the literature reported example, and from these results the most promising system for FFF printing has been identified. Fibres of this LCE have been extruded, and their mechanical properties and UV response tested.
[1] Petr, M.; Katzman, B.-a.; DiNatale, W.; Hammond, P. T., Macromolecules, 2013, 46, 2823-2832
4:30 PM - SM8.9.06
Programming Stimulus Response in Chromonic Liquid Crystal Hydrogels
Ruvini Kularatne 1 , Taylor Ware 1
1 , University of Texas at Dallas, Richardson, Texas, United States
Show AbstractDirected self-assembly of stimuli-responsive materials is a promising strategy to create active biomaterials. In this work, we aim to control the mechanical properties and stimuli-responsive behavior of hydrogels using the directed aggregation and self-assembly of lyotropic chromonic liquid crystals. Specifically, we will discuss the synthesis, structure, and characterization of anisotropic, mechanically-active hydrogels based on ionic, dimethacrylate derivatives of perylene diimide, which exhibit lyotropic chromonic liquid crystal phases. These chromonic monomers can be aligned macroscopically using textured surfaces. After alignment, the monomer mixtures are then polymerized into anisotropic hydrogels. Recent results indicate that when hydrogels are polymerized in the aligned chromonic state, the swelling of these gels is nearly 4x larger along the nematic director than perpendicular to the director. By copolymerizing chromonics with responsive comonomers, such as n-isopropylacrylamide, these anisotropic gels can be rendered shape-responsive to stimuli such as small temperature changes. This shape change behavior will be discussed and correlated to the polymer network structure, morphology, and liquid crystalline phase. By designing the nematic director in these materials, films that morph from flat to complex 3D shapes can also be designed. Finally, these programmable, anisotropic gels will also be discussed in the context of future applications in biomedical devices.
4:45 PM - SM8.9.07
Shape-Memory Cryogels Based on Conformational Transition of Peptides
Zewang You 1 2 3 , Marc Behl 1 3 , Andreas Lendlein 1 2 3
1 , Institute of Biomaterial Science, Helmholtz-Zentrum Geesthacht, Teltow Germany, 2 Institute of Chemistry, University of Potsdam, Potsdam Germany, 3 , Joint Laboratory for Biomaterials and Regenerative Medicine, Tianjin University-Helmholtz-Zentrum Geesthacht, Teltow Germany
Show AbstractShape-memory hydrogels have attracted significant interest as soft smart materials to be potentially applied in tissue engineering applications. A current challenge for these materials is the implementation of other stimuli than heat. Furthermore, swelling of the shape-memory hydrogels once the shape-memory effect occurred should be avoided. Our approach to address these challenges was a cryogel prepared from a bifunctional hydrophilic poly (ethylene glycol) diisocyanatoethylmethacrylate (PEGdiIEMA, Mw = 4000 g/mol) as crosslinker and switching segments from peptides (methacrylated-VKVKVKVKVpPTKVKVKVKV-NH2) incorporated as switching segments, which enable the fixation of a temporary shape by a change of conformation between random coil and β-sheet. Cryogels with peptide concentrations between 1 wt% and 4 wt% were prepared and their shape-memory properties quantified in bending tests. In these cryogels the gel contents ranged from 66% to 87% indicating a successful crosslinking reaction. When the peptide concentration was raised, the volumetric degree of swelling increased from 2100 Vol% to 3100 Vol%, whereas the storage moduli of 0.4-2.7 KPa were in the range of soft materials. The porous structure of the cryogels was capable to provide shape stability of the permanent shape. At a pH above 9, the peptide side chains adopted predominantly β-sheet confirmation as shown by Infrared spectroscopy and acted as additional temporary netpoints fixing a temporary shape, while when the pH was changed to below 7 they disassembled and transitioned back to random coil conformation causing recovery of the permanent shape. Shape fixity ratios up to 90% were realized and increased when the peptide concentration was increased as well, while the shape recovery ratios were in the range of 90-98%. In summary, a new mechanism to trigger the shape-memory effect was implemented into hydrogels and the concept provides a new direction for the design of stimuli-sensitive hydrogels.
5:00 PM - *SM8.9.08
Macromolecular Metamorphosis
Brent Sumerlin 1 , Hao Sun 1 , Christopher Kabb 1 , Yuqiong Dai 1 , Megan Hill 1 , Abhijeet Bapat 1
1 George & Josephine Butler Polymer Research Laboratory, Center for Macromolecular Science & Engineering, Department of Chemistry, University of Florida, Gainsville, Florida, United States
Show AbstractThis presentation will focus on our recent advances in the areas of dynamic-covalent materials and responsive nanoparticles. By relying on a variety of reversible covalent reactions that lead to readily cleaved bonds, we have prepared materials that combine the physical integrity of covalent materials and the structural dynamics of supramolecular complexes. Oximes, boronic esters, boronate esters, and Diels-Alder linkages have all been employed to prepare these responsive and dynamic materials, with particular attention having been dedicated to the preparation of hydrogels, elastomers, and nanoparticles. We seek to exploit the reversible nature of these bonds to prepare responsive and self-healing materials. We have also exploited the dynamic nature of these systems to prepare macromolecules that undergo dramatic transformations in architecture when triggered.
5:30 PM - SM8.9.09
Programming Temporal Shapeshifting
Xiaobo Hu 1 , Jing Zhou 1 , Mohammad Vatankhah-Varnoosfaderani 1 , William Daniel 1 , Qiaoxi Li 1 , Aleksandr Zhushma 1 , Andrey Dobrynin 2 , Sergei Sheiko 1
1 , University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States, 2 Department of Polymer Science, University of Akron, Akron, Ohio, United States
Show AbstractShapeshifting enables a wide range of engineering and biomedical applications, but until now transformations have required external triggers. This prerequisite limits viability in closed or inert systems and puts forward the challenge of developing materials with intrinsically encoded shape evolution. Herein we demonstrate programmable shape-memory materials that perform a sequence of encoded actuations under constant environment conditions without using an external trigger. We employ dual network hydrogels: in the first network, covalent crosslinks are introduced for elastic energy storage, and in the second one, temporary hydrogen-bonds regulate the energy-release rate. Through strain-induced and time-dependent reorganization of the reversible hydrogen bonds, this dual network allows for encoding both the rate and pathway of shape transformations on time scales from seconds to hours. This generic mechanism for programming trigger-free shapeshifting opens new ways to design autonomous actuators, drug-release systems, and active implants.
5:45 PM - SM8.9.10
Characterizing Shape-Memory Effects of Polymeric Micro-Scale Objects
Karl Kratz 1 , Yue Liu 1 2 , Yi Jiang 1 2 , Liang Fang 1 3 , Andreas Lendlein 1 2
1 Institute of Biomaterial Science, Helmholtz-Zentrum Geesthacht, Teltow Germany, 2 Institute of Chemistry, University of Potsdam, Potsdam Germany, 3 State Key Laboratory of Materials-Oriented Chemical, College of Material Science and Engineering, Nanjing China
Show AbstractThe ongoing trend of miniaturizing multifunctional devices, especially for applications in minimally-invasive medicine or in sensors, demands new strategies for designing the required functional polymeric micro-components or micro-devices. Here, polymers, which are capable to actively move in response to an external stimulus like shape-memory polymers, are intensively discussed for realization of multifunctional micro-components. In this context, a better understanding of the underlying working principles for functionalization of polymeric micro-scale objects with shape-memory effects, are required.
In the current study, we explored the shape changing capability of microstructured polymeric substrates and micro-cuboids prepared from crosslinked poly[ethylene-ran-(vinyl acetate)] (cPEVA). We investigated the shape-memory effects of such micro-scale cPEVA objects on both micro- and nanolevel by optical microscopy and atomic force microscopy. The structured cPEVA substrates consisted of an array of micro-cylinders with a height of 10 µm and a diameter of 25 µm, while the micro-cuboids had an edge length of 25 µm and a height of 10 µm. During programming, the microstructured substrates were compressed resulting in films having a nano-smooth surface. For micro-cuboids, different degrees of compression were applied. Excellent shape-memory properties, characterized by a complete recovery of their initial shapes at micro- and nanoscale were obtained upon heating for both microstructured substrates and micro-cubiods. These findings are demonstrating the general applicability of the presented technology to serve either as active surface structure or as actuating microcomponents in technical or medical devices.
References
Jiang, Y.; Fang, L.; Kratz, K.; Lendlein, A., Influence of Compression Direction on the Shape-Memory Effect of Micro-Cylinder Arrays Prepared from Semi-Crystalline Polymer Networks. MRS Advances 2016, 1 (27), 1985-1993.
SM8.10: Poster Session III: Advanced Polymers
Session Chairs
Axel Neffe
Nicola Tirelli
Friday AM, April 21, 2017
Sheraton, Third Level, Phoenix Ballroom
9:00 PM - SM8.10.01
Micellization and Phase Separation of Poly(ethylene oxide)-Poly(propylene oxide) Alternating Multiblock Copolymers in Water
Yukiteru Katsumoto 1 , Tasuku Horiuchi 2 , Kazuaki Rikiyama 2 , Yusuke Sanada 1
1 , Fukuoka University, Fukuoka Japan, 2 Graduate School of Science, Hiroshima University, Higashi-Hiroshima, Hiroshima, Japan
Show AbstractAmphiphilic block copolymers have attracted keen interests for many decades because of the potential use as nonionic macromolecular surfactants and drug carriers. In contrast to PEO-PPO-PEO triblock copolymers, which are known as Pluronic or Poloxamer, the effects of alternating multiblock (AMB) copolymers on the solution properties have been much less investigated. In this study, we focus on the micellization and phase behavior of the PEO-PPO AMB copolymers in water.
The turbidity measurement has been carried out for monitoring the cloud point (Tc). Tc of the aqueous solution of the AMB copolymer is much lower than that of Pluronic with the same PEO/PPO content. The concentration dependence of Tc clearly indicates that the polymer aqueous solution undergoes the phase separation with a lower critical solution temperature. The transmittance of the 350 light for the 2.0 wt% aqueous solution of the PEO-PPO AMB copolymer shows a small decrement at the region from 30 to 40 °C before the large drop concerned with Tc. This suggests that AMB copolymers form a micelle or small aggregate below Tc.
The DLS measurement clarifies that the particle size distribution (PSD) of the 5×10-6 M solution at 25 °C is bimodal, in which one peak appears at ca. 10 nm of the hydrodynamic radius (Rh), which is assignable to the unimer, and the other is located at ca. 200 nm. The fluorescent probe method reveals that the large aggregate does not have the hydrophobic core, indicating that there is no micelle at 25 °C and 5×10-6 M. As the temperature goes up, however, PSD becomes a unimodal at around 40 °C. In the range from 40 to 50 °C, the peak of Rh = 20 nm does not show any temperature dependence. The fluorescent probe method suggests that the 20 nm aggregates have the hydrophobic core like a micelle. The micellization is also supported by the surface tension measurements.
The characteristics of the AMB configuration for amphiphilic copolymers are the following; (i) a low critical micelle concentration (< 10-5 M), (ii) a less population of unimer coexisting with micelle, and (iii) a low Tc of the aqueous solution.
9:00 PM - SM8.10.02
Stress-Sensing Thermoset Polymer Network via Grafted Cinnamoyl/Cyclobutane Mechanophore Units in Epoxy
Ryan Gunckel 1 , Elizabeth Nofen 1
1 , Arizona State University, Tempe, Arizona, United States
Show AbstractWithin the field of mechanochemistry, the study of mechanophores – molecular units responsive to external application of force – incorporated into networked thermosets has been limited, instead focusing on thermoplastic and elastomeric polymers. Thermosets provide an excellent opportunity for the development of mechanochemistry due to their wide applications in circuitry, adhesives, protective equipment, coatings and many others. Utilizing novel grafting methods, force-responsive cinnamoyl moieties were covalently incorporated into an epoxy thermoset via two separate methods. Cinnamamide, a mechanophore precursor, was grafted onto a traditional epoxy resin, allowed to cure via hardener addition, and UV irradiated to dimerize the cinnamoyl units. The other approach utilized the pre-irradiation of cinnamamide in solution to form dimerized cinnamamide before being grafted onto the epoxy resin and cured via hardener addition. Breaking of these force-sensitive cyclobutane rings within dimerized cinnamoyl groups occurs under a compressive strain, which was then evaluated by observing the fluorescence intensity increase and correlating with the applied stress. After successful incorporation of these mechanophores, the retention of mechanical and thermal properties were evaluated for the composites. Both methods showed a statistical increase in intensity at 6% strain, immediately after the yield point of the materials. While both samples show a decrease in both mechanical and thermal properties, samples containing pre-irradiated cinnamoyl moieties showed more property retention than samples irradiated after addition of hardener. Overall, both methods were successful in incorporating a grafted mechanophore into an epoxy network capable of damage sensing via fluorescent emission.
9:00 PM - SM8.10.03
Early Damage Detection of Epoxy via Poly(vinyl Cinnamate) Mechanophore Using Fourier Transform Infrared Spectroscopy
Ryan Gunckel 1
1 , Arizona State University, Tempe, Arizona, United States
Show AbstractThe employment of mechanophores and mechanochemistry in materials has allowed for many novel, force-responsive materials to be developed. Applications of these materials has a large scope, including the capability of early damage detection to prevent failure of important equipment. Studies exploring the force sensing capabilities of the UV-dimerized cinnamoyl moiety have shown that after severing its cyclobutane bond through application of an external force, this moiety will revert back to its initial fluorescent state. Current fluorescent detection methods, however, fail to properly detect damage in highly opaque samples. ATR-FTIR offers the ability to measure a composite’s chemical structure at the surface of the material and examine activation of the cinnamoyl moiety’s cyclobutane bond, regardless of sample transparency. Samples containing 10 wt% poly(vinyl cinnamate) as the active mechanophore, as well as set of samples with an additional 0.5 wt% carbon nanotubes to create a completely opaque composite, were synthesized. Both composites showed an increase in peaks at 1650 cm-1 and 1635 cm-1 after strain, which correspond to the cis and trans isomers of the fluorescent double-bond in the cinnamoyl group. A statistical difference in peak height occurs as early as 4% strain – before the yield point of the composites – indicating that early signal detection is possible. This improved sensing method provides a simpler, faster method for early signal detection over fluorescent imaging due to the wider availability of FTIR analysis.
9:00 PM - SM8.10.04
Mechanical Properties of Poly(Lactic Acid) Composites Reinforced with CaCO3 Eggshell Based Fillers
Nicholas Betancourt 1 , Duncan Cree 1
1 , University of Saskatchewan, Saskatoon, Saskatchewan, Canada
Show AbstractPoly(lactic acid) (PLA) bioplastics are recyclable and biodegradable thermoplastics. They are derived from environmentally friendly sources such as potatoes, cornstarch and sugarcane. However, PLA is inherently brittle with low impact strength. The goal of this study is to improve mechanical properties of PLA by the addition of calcium carbonate (CaCO3) fillers. PLA composites were prepared by injection molding conventional limestone (LS) and white chicken eggshell (WES) powders with particle sizes of 63 μm and 32 μm in amounts of 5 wt. %, 10 wt. % and 20 wt. %. Mechanical properties such as, tensile strength, tensile modulus, and Charpy impact strength were investigated. For both particle sizes, the tensile strength decreased as the filler content increased, but was highest for a filler loading of 5 wt. %. In general, the 32 μm powder fillers had better tensile strengths than 63 μm sized fillers. The tensile modulus increased with filler content and was highest at 20 wt. % for both particle sizes. When 10 wt. % and 20 wt. % LS powder (32 μm) were added, the impact strength was improved by 3.9 % and 1.0 %, respectively. Other formulations tended to embrittle the composites. The particle filler morphology and fractured surfaces were observed by scanning electron microscopy (SEM) and determined to have well dispersed particles with smooth fractured surfaces. Water absorption behavior of PLA/CaCO3 composites were studied by immersion in distilled water at room temperature for 56 days. Pure PLA absorbed the least amount of water while the water absorption of CaCO3 composites were a function of powder type and content.
9:00 PM - SM8.10.05
Vapor Phase Synthesis of Nanoparticles in Fluoropolymers—Connections between Particle Size Distribution and Polymer Free Volume
Fan Zeng 1 , Daphnee Chapelle 1 , Dajie Zhang 1 , James Spicer 1
1 , Johns Hopkins University, Baltimore, Maryland, United States
Show AbstractA modified, chemical vapor, infusion technique has been used to synthesize polymer matrix nanocomposites. Depending on the precursors and processing conditions, various metal or metal-oxide nanoparticles exhibiting photochromic or photocatalytic behaviors have been directly grown in fluoropolymer matrices. These matrices display excellent optical transparency and stability under UV irradiation and as a result, chemo-optical properties of the nanocomposite depend almost entirely on the action of the embedded nanoparticles. Palladium acetylacetonate has been used as precursor to form palladium nanoparticles in perfluoroalkoxy alkane. Particle radius ranging approximately from 1 to 4 nm has been observed for a single infusion process. Contrary to most solution-processed nanocomposites, Oswald ripening was not observed but highly-dispersed nanoparticles with narrow particle size distributions were found in these materials. Transmission electron microscopy analysis indicates that particle size and spatial distributions are affected by processing conditions and appear to be correlated with the free volume of the polymer matrix. While the particle size distribution of the nanocomposites processed at low temperatures has a characteristic positive skew, surface percolation of nanoparticles has been observed for those processed at relatively high temperatures. The effect of temperature on polymer free volume has been investigated and is believed to play an important role in this percolation phenomenon.
9:00 PM - SM8.10.06
Low Bandgap Poly(Fluorinated Metallophthalocyanine-Alt-diketopyrrolopyrrole)s with Outstanding Thermal Stability
Sunmi Hong 1 , Anil Kumar Mutyala 1 , Namhyeon Kim 1 , Jong Seung Park 1
1 , Department of Organic Material Science and Engineering, Busan Korea (the Republic of)
Show AbstractOver the past years diverse electron donor-acceptor (D-A) conjugates have been designed, synthesized, and investigated. Among the various D-A architectures, phthalocyanines (Pc), as an extended electron-rich aromatic moiety containing 18 p-electrons, hold an exceptional position due to their outstanding physicochemical properties and high molar extinction coefficients in the red to near infrared region. However, very few examples of trans-disubstituted Pc subunits being connected through π-conjugated pathways have been described and investigated for expanding the use of these materials for useful optoelectronic applications. As far as we know, no conjugated D-A alternating polymerization based on covalent reactions on Pcs has been achieved, which restricts the final structure to rather simple architectures. Meanwhile, derivatives of diketopyrrolopyrrole (DPP) are frequently employed as acceptors in molecular D-A systems due to their exceptional absorbance properties in the long wavelength region, strong fluorescent performance, and high thermal stability. Therefore, it has been intuitively envisaged that conjugated alternating D-A polymers based on Pc and DPP can offer excellent ambient stability, accompanied by strong absorption properties and high charge transport efficiency.
Here we report the synthesis of a novel zinc-phthalocyanine (ZnPc)-diketopyrrolopyrrole (DPP) ambipolar polymer containing two bulky bis(trifluoromethyl)phenyl groups at the nonperipheral positions on Pc. Our synthetic procedure was designed for polymerization of alternating subunits in a Suziki-Miyaura cross-coupling reaction to iodo-ABAB-Pc with DPP-boronic acids. It is reasonably envisaged that this alternating subunits should provide a linearly conjugated alternating polymer backbone made of Pc and DPP. The resulting Pc-DPP alternating polymers exhibit a low bandgap of around 1.7 eV and the highest level of thermal stability. Owing to the potential intriguing properties of these compounds, they find promising applications in electronic and optoelectronic devices.
9:00 PM - SM8.10.07
The Pigment Eumelanin as a UV-Protection Enhancer of Packaging Films—A First Screening
Eduardo Di Mauro 1 , Richard Silverwood 1 , Abdellah Ajji 1 , Fabio Cicoira 1 , Clara Santato 1
1 , Polytechnique Montreal, Montreal, Quebec, Canada
Show AbstractThe current effort of the scientific community to reduce greenhouse gas emissions and decrease the amount of waste materials in landfills relies on the replacement of plastic materials made from non-renewable resources with bio-based and biodegradable materials. Such endeavour concerns materials for food packaging and food service, too [1]. Organic and inorganic additives are used to improve the functional properties (such as mechanical and oxidation stability and the barrier properties) of packaging materials [2]. Understanding the UV-radiation exposure in the end-use or storage environments of the food, and, consequently, reducing the resulting UV-radiation induced damage, is a key aspect of the packaging science and engineering [3]. Eumelanins are a dark-brown subclass of the melanins, biopolymers present in animals and plants [4]. Important properties of melanin are metal ion chelation [5], biocompatibility, biodegradability [6], mixed ionic-electronic conduction and photoprotection [5]. In particular, eumelanin presents a broad-band optical absorption, that is, a monotonic featureless absorption increase from the ultraviolet to the near-infrared (NIR) [5]. Leveraging on its excellent photoprotection properties, we herein report on the novel possibility of using eumelanin as a biodegradable UV-protection enhancer for biodegradable packaging films. Two types of biopolymers were combined with eumelanin, poly(lactic acid) (PLA) and polybutyrate-adipate-terephtalate (PBAT), as they require less harsh processing temperatures, that would preserve the pigment’s properties, and present better biodegradability than more “conventional” polymers (e.g. polyamides) [1]. The packaging films were obtained by film casting, and the pigment was added in different weigh percentages (0.5, 1 and 5% wt.). Different types of melanins were exploited: synthetic (commercial Sigma and non-commercial DHI-melanin, DHICA-melanin) or natural (extracted from the ink of a cuttlefish). The UV-absorption without and with the addition of the different types of pigments in different percentages was performed for the two biopolymers. Furthermore, the optical properties that could be affected by eumelanin’s presence were evaluated: (i) Color; (ii) Haze and (iii) Gloss. Other crucial properties are being evaluated, such as Barrier Testing (O2, Water Vapors), Durability as well as Package Integrity and Seal Strength of the packaging films. Our research represents a further step towards achieving biocompatible and biodegradable film packaging materials. [1]V. Siracusa et al., Trends Food Sci. Technol., 19, 12, 634–643, 2008;[2]A. Sorrentino et al.,Trends Food Sci. Technol., 18, 2, 84–95, 2007;[3]L. K. Krehula et al., Polym. Bull., 2016; [4]M. d’Ischia et al., Pigm Cell Melanoma R, 26, 5, 616–633, 2013;[5]J. Wuensche et al., Adv. Funct. Mater., 23, 45, 5591–5598, 2013;[6]C. J. Bettinger et al., Biomaterials, 30, 17, 3050–3057, 2009
9:00 PM - SM8.10.08
Acoustic Characteristics and Thermal Conductivity of Polycarbonate/Graphite Intercalation Compound
Sung-Ryong Kim 1 , Young Han Bae 1 , Min Ji Yu 1 , Kwang Min Park 2
1 , Korea National University of Transportation, Chungju Korea (the Republic of), 2 , Seil Hitec Company, Cheongwon Korea (the Republic of)
Show AbstractGraphite intercalation compound (GIC) contained polycarbonate composites were prepared by melt mixing and the effects of GIC and its surface treatment using oleylamine (OA) on the morphology, and properties of the polycarbonate based composites were examined. As increasing the GIC contents, the sound absorption coefficient and sound transmission loss of the PC/GIC composites increased over the frequencies of 500~ 4000 Hz. The OA treatment of GICs improved the interfacial bonding and dispersion of GICs in the PC matrix and it allowed less voids and the smoother fractured surface compared to the PC composites with the untreated GIC fillers. Compared to bare PC, the PC/GIC (20 wt%) composites showed the higher absorption coefficient at 4000 Hz. The absorption coefficient at 4000 Hz, sound transmission loss, and thermal conductivity of the PC/GIC (20 wt%) composites were 0.08, 34 dB, and 1.12 W/mK, respectively. At 20 wt% of GIC loading, the sound transmission loss at 2000 Hz increased to 39 dB from 12 dB of the bare PC. This results indicate that the PC/GIC composites with lower surface density could be more suitable compared to the stainless steel in the fields which require the sound absorption and sound blocking with a light weight.
9:00 PM - SM8.10.09
Electrospun Nanofibrous Scaffolds—Towards Enhanced Tissue-Engineered Heart Valves
Dina Ibrahim 1 , Ahmed Youssef 2 , Andreas Kakarougkas 4 , Nageh Allam 3
1 Biotechnology Program, Energy Materials Laboratory (EML), School of Sciences and Engineering, American University in Cairo, New Cairo Egypt, 2 Packing and Packaging Materials Department, National Research Center, Cairo Egypt, 4 Biology Department, School of Sciences and Engineering, American University in Cairo, New Cairo Egypt, 3 Energy Materials Laboratory (EML), School of Sciences and Engineering, American University in Cairo, New Cairo Egypt
Show AbstractHeart valve diseases lead to the death of 492,042 patients in the developing world and 20,000 patients in the US annually. Improving the life expectancy of the patients is done through replacing the diseased valves with mechanical or biological valves. However, both of them have major drawbacks. Hence, TEHVs have emerged to be the ideal substitute. TEHVs are biodegradable, biocompatible and mechanically stable scaffolds that resemble native valves. These scaffolds are seeded with autologous cells and conditioned in a bioreactor prior to implantation. There are many techniques to fabricate such scaffolds, however electrospun nanofibrous scaffolds are considered the golden standard.
Electrospinning is a versatile fabrication technique that produces scaffolds that resemble the natural extra-cellular matrix of the native valves. There are two type of polymers that can be electrospun: natural and synthetic. Synthetic polymers are considered superior because their physical and mechanical properties can be controlled. In addition, they have varied degradation rate. Synthetic polymers that have been used so far to fabricate electrospun scaffolds for TEHVs include: PLA, PGA and their copolymers, PHA, PCL and PGS. All of the aforementioned polymers have drawbacks that render them far from being ideal materials for TEHV scaffolds.
PGS was reported recently as a good candidate for soft tissue engineering, however it has some limitations. Herein, we are working on a modified form of the PGS mixed with another polymer that can be electrospun into nanofibrous scaffolds. The resulting scaffolds are expected to overcome the limitation accompanied with the already reported PGS scaffolds in literature. In addition, the scaffolds will have different surface topographies that is expected to enhance the cellular attachment.
The outline of this work is divided into two parts: (A) Polymer synthesis and scaffolds fabrication followed by: chemical and physical characterization, mechanical characterization degradation and swelling tests. (B) Biological assessment. The modified polymer was successfully synthesized and characterized. The current ongoing work is concerning scaffolds fabrication using blend of the two proposed polymers.
9:00 PM - SM8.10.10
Processing Agarose Films and Foams for Biomedical Applications
Mishal Patel 1 , Joshua Kaufman 1 , Alexander Cole 1 , Sean Moore 1 , Ayman Abouraddy 1
1 , University of Central Florida, Orlando, Florida, United States
Show AbstractWith applications ranging from food packaging to wound dressings to local drug delivery, polymeric films and coatings have been used in industry and investigated in the lab for decades. Processing techniques on well-chosen materials can yield mechanically stable films with a wide range of diffusion, degradation, and surface energy characteristics that are flexible enough to conform to most contours. Petroleum-based polymers such as the widely used and various PLGA species often require harsh chemicals to process which are difficult or impossible to completely remove, which is undesirable for applications in the food and medical industries. Furthermore, recent cultural shifts in environmental attitudes toward green, renewable materials may cause both consumers and investors to shy away from petroleum-based products. In light of these factors, we have developed a fabrication method for producing free-standing agarose films and gauze-like foams.
Agarose is the polysaccharide derived from certain forms of red algae whose gelatin agar is used ubiquitously in microbiology laboratories and even cooking. Our process begins by boiling agarose in water to completely dissolve it. It is then allowed to cool and solidify into a gel disk that is then placed under vacuum at room temperature until the gel is completely dehydrated, forming a flexible, sturdy, free-standing film. The diameter and thickness of the resulting film may be tuned by allowing the solution to gel in a larger beaker and adjusting the volume of the gel disk at the outset. Molds may be used to produce various shapes, and the films are easily cut by scissors or a razor blade to further alter the geometry. The mechanical properties may be tuned by adding polyethylene glycol (PEG) to the original solution, resulting in a film that is more flexible with more elongation under stress. Adding cargo is simply achieved by pipetting a small amount of aqueous solution containing the cargo to the gel before dehydration and allowing the gel to soak up the cargo in a sponge-like manner at room temperature. The release rate of the cargo is tunable by the introduction of the polysaccharide chitosan to the gel. We demonstrate this ability by altering the release rate of fluorescein into water from minutes to hours. Furthermore, multi-stage release is possible by producing multi-layered films, which is demonstrated through an experiment in which a quick burst of fluorescein is followed by slow, sustained release. Lastly, if the initial solution is instead slowly cooled while continuously stirred, the gel takes on the consistency of applesauce, which if dried under vacuum forms a porous foam. We demonstrate the ability to control the porosity of the foam by varying the speed of dehydration under vacuum. The same control over the release rate of cargo is demonstrated, as well as the additional benefit of better absorption of aqueous solutions than the dry gel films, for possible use as a drug-eluting gauze.
9:00 PM - SM8.10.11
Structural, Thermal, Mechanical and Microbiological Properties of PMMA-Ag Nanocomposites
Francisco Souza Neto 1 , Anielly Melo 2 , Renan Fernandes 3 , Douglas Monteiro 3 , Edson Leite 1 , Debora Barros Barbosa 3 , Emerson Camargo 1
1 Department of Chemistry, Federal University of Sao Carlos, Sao Carlos, SP, Brazil, 2 Department of Agrochemistry, Federal Institute Goiano, Rio Verde Brazil, 3 Department of Pediatric Dentistry and Public Health, State University of São Paulo, Araçatuba Brazil
Show AbstractCurrently, approximately 50–70% of the denture wearers present pathogenic state known as denture stomatitis, i.e., an inflammatory process caused by the Candida albicans. The silver nanoparticles have been effectively employed as antimicrobial agent because their large surface area allows the exposition of micro-organisms. Moreover, silver nanoparticles have been incorporated in different polymers to medical applications, specially the Poly(methyl methacrylate) (PMMA). The PMMA is an acrylic resin biocompatible used in the anchorage of prosthetic joint components due to its long-term permanence and it is not able to cause adverse reactions to the human health. Thus, the PMMA/Ag nanocomposites can be used as potential candidates for dental prosthesis. Therefore, the aim of our study was estimate the effect of the insertion of different concentrations of silver nanoparticles in a commercial acrylic resin for dental application. The silver nanoparticles were synthesized by the Turkevich method, and PMMA was obtained by the thermal polymerization of Lucitone 550 acrylic resin, according to manufacturer’s instructions. The PMMA/Ag nanocomposites were synthesized by adding 0.05, 0.5 and 5% volume/weight of silver nanoparticles to the polymer during the thermal polymerization stage. The phase structure was analyzed by means of Raman and nuclear magnetic ressonance spectroscopies employing 13C-CPTOSS. The Raman spectra showed typical absorption bands of PMMA and NMR revealed 5 peaks characteristics of the PMMA. The scanning electron microscopy micrographs evidenced the presence of a homogeneous distribution of silver particles with spherical shapes and sizes of about 20 nm. The thermogravimetric analysis demonstrated that higher silver concentrations improves the thermal stability of PMMA/Ag nanocomposites because the barrier effect. The decrease in the glass transition temperature in PMMA/Ag nanocomposites, when compared the pure PMMA, indicated an increase in the polymeric chains mobility confirmed by dynamic mechanical thermogravimetric analysis. These results indicated a β relaxation, which involves the ester side group occurring around the room temperature, and the glass transition, predominantly involving the main chain dynamics at around 110°C for PMMA, and decreasing for nanocomposites which are characteristic of materials which exhibit an interfacial interaction between inorganic nanoparticles with polymer matrix. Clinically, the nanocomposites can be applied in dentistry, according to the normative American Dental Association (1958), through its specification No. 12 and ISO 4049, which evaluate the mechanical properties of dental materials. These results showed statistically are not difference between nanocomposites and the polymeric matrix. The microbiological adhesion test of PMMA and its nanocomposites to combat Candida glabrata revealed the nanocomposite with a lower percentage of colloidal solution have higher fungicide activity.
9:00 PM - SM8.10.14
Design and Characterization of sub-10 nm Metal Nanoparticle-PVDF Nanocomposite Based Solid-State Dielectric Material
Anju Toor 1
1 , University of California, Berkeley, Berkeley, California, United States
Show AbstractMaterials with high dielectric constants have drawn increasing interests in recent years for their important applications in capacitors, actuators, and high energy density pulsed-power. Particularly, polymer-based dielectrics, owing to their properties like high electric breakdown field, low dielectric loss, flexibility and easy processing are excellent candidates. In order to enhance the dielectric constant of polymer materials, typically, high dielectric constant fillers materials are added to the polymer. Previously, ferroelectric and conductive fillers have been mainly used. However, such systems suffered from various limitations. For example, composites based on ferroelectric materials like Barium Titanate exhibited high dielectric loss and poor saturation voltages. Conductive fillers based composites exhibited significant dielectric loss due to the presence of particle agglomerates.
This article reports the enhanced dielectric properties of a nanocomposite material containing sub-10 nm coated metal nanoparticles (NPs). Nanometric sized high dielectric constant particles are attractive candidates for their use as fillers in dielectric nanocomposite materials due to their high interfacial area. These metal particles will result in an enhancement in electric permittivity due to the interfacial polarization. Further, since the ligand coating provides local electrical resistance, these nanoparticles can still be incorporated at a high volume ratio in the polymer scaffold without causing an increase in dielectric loss.
A novel nanocomposite material is designed and synthesized using polyvinylpyrrolidone (PVP) functionalized gold nanoparticles embedded inside a polyvinylidene fluoride (PVDF) polymer matrix. Scanning electron microscopy (SEM), atomic force microscopy (AFM), transmission electron microscopy (TEM) and wide angle X-ray scattering (WAXS) techniques were used for the characterization of the nanocomposite material.
A homogeneous dispersion of gold nanoparticles with no particle agglomeration has been achieved upto 15 wt% of gold nanoparticles. Fabricated nanocomposite films showed the absence of voids and cracks. It is important to minimize the number of voids as these air-trapped pockets result in the reduction of dielectric breakdown strength. Dielectric characterization of the nanocomposite material with 15 wt% nanoparticle content showed a 2 times enhancement in the dielectric constant over the base polymer with a dielectric loss value of 14% at 1kHz.
9:00 PM - SM8.10.15
Self-Immolative Dendrimer as a Hypoxia-Sensitive Fluorescent Imaging Probe
In Jae Chung 1 , Cheol-Hee Ahn 1
1 Research Institute of Advanced Materials (RIAM), Department of Materials Science and Engineering, College of Engineering, Seoul National University, Seoul Korea (the Republic of)
Show AbstractSelf-immolative Dendrimer has well defined 3-D branched structure with designed for controlled release of various molecules. End group of conjugated molecules undergo domino-like degradation by single triggered event of self-immolative dendrimer. Triggered reaction makes release of modified peripheral groups and dendrimer building block, which enable signal amplification to boost diagnostic signal which able to apply high sensitive bio imaging and sensor application. Making use of these characteristic, we expect to display advantage in accessing and deliver a lot of molecules to hypoxic region in solid tumor.
Hypoxic condition means insufficient oxygen to metabolish, generally expressed in stroke, inflammation and most solid tumors. Most solid tumor has chronic hypoxic condition because they outgrow their vascular supply, which provides the conditions of low oxygen level and abnormal tumor tissue environment. In hypoxic condition, solid tumors promote reductive processes and stimuli-sensitive materials utilizing the bioreductive conditions can be applied for an activatable sensing system at a specific region. Dendrimer has relatively small hydrodynamic volume than same molecular weight polymer, so we expect to display advantage in accessing hypoxic region in solid tumor which located far from blood vessls (150 um). In this study, we synthesize a self-immolative dendrimer to apply florescence imaging probe. Nitro group was modified at dendrimer core to introduce hypoxia-sensitivity, and dendritic structure was conjugated by carbamate linkage to enable cascade degradation. Finally, fluorescent dye was conjugated at periphery of dendrimer to apply fluorescent imaging. At hypoxic condition, nitro group was reduced and self-immolative reaction was sequentially progressed through carbamate linkage. Such change resulted in the release of fluorescence dyes conjugated at the periphery of dendritic building blocks and produce a hypoxia-sensitive fluorescence imaging probe.
9:00 PM - SM8.10.16
Effect of Siloxane-Terminated Side-Chains on the Electrochromic Properties of Benzotriazole-Bearing Donor-Acceptor Type Conjugated Polymers
Namhyeon Kim 1 , Sivalingam Suganya 1 , Sunmi Hong 1 , Da-Hye Kim 1 , Jong Seung Park 1
1 , Department of Organic Material Science and Engineering, Busan Korea (the Republic of)
Show AbstractThe usefulness of conjugated polymers (CPs) has provided a space for multiple applications, including organic light emitting diodes, organic field effect transistors, organic solar cells, and electrochromic (EC) devices. The attractive properties of CPs are mostly based on the ability to manipulate the electronic and spectral properties by way of chemical and structural modifications. Especially, the optical transitions, depending on redox potentials from neutral to oxidized state, are critically important for their use as EC materials. Most EC polymers exhibit noticeable optical transitions when electrochemically modified, giving rise to a strong absorption bands in the visible regions. In that regard, conjugated polyheterocyclic polymers such as polyaniline, poly(3,4-ethylenedioxythiophene) (PEDOT), poly(3,4-propylenedioxythiophene) (PProDOT), and their derivatives have been widely investigated mainly due to high conductivity originated from low bandgap and facile optical modulation. However, it is noteworthy to mention that, compared to numerous attempts to introduce new conjugated backbone structures for EC applications, the side-chain engineering of EC polymers has been rarely investigated.
Herein, we report the synthesis and electrochromic applications of benzotriazole-bearing donor-acceptor (D-A) type conjugated polymers featured with siloxane-terminated alkyl chains. Specifically, we focus on the effect of solubilizing side-chains by adopting a hybrid siloxane-terminated unit on the spectral and electrochemical performances of EC polymers. These D-A type CPs have been prepared by combining electron-accepting benzotriazoles and electron-rich thiophene or di-thiophene via the Stille coupling reaction. Among various acceptors, we have been intrigued by benzotriazole moiety due to the presence of two electron-withdrawing imine (C=N) functionalities, which significantly enhance the electron transporting ability. Incorporating hybrid siloxane-solubilizing groups is expected to influence the intermolecular interactions between adjacent polymer chains. Moreover, the presence of long alkyl side-chain allows high molecular weight, and contributes to the increased solubility of the resulting polymers in most common organic solvents. With this in hand, various EC devices employing D-A type CPs have been designed and fabricated. The detailed results of the present work will be presented in the conference.
Keywords: Donor-acceptor, conjugated polymer, benzotriazole, siloxane side-chain, electrochromic device, electrochromic polymer
9:00 PM - SM8.10.17
Biosensors based on Conducting Polymer Scaffolds Targeting Carbohydrate-Protein Interactions
Abdul Rehman 1 , Sami Nazib 1
1 , KFUPM, Mississauga, Ontario, Canada
Show AbstractStudying carbohydrate−protein interactions is challenging because of the complexity and heterogeneity of the cell surface, the inherent structural complexity of carbohydrates, and the typically weak affinities of the binding reactions between the lectins and monovalent carbohydrates. In contrast, label-free biosensors allow real-time monitoring of carbohydrate−protein interactions in their natural states.
We illustrate that functionalized glycosylated conductive polymer scaffolds are the ideal multimodal biointerfaces that not only simplify the immobilization process for surface fabrication via electrochemical polymerization but also enable the simultaneous analysis of the binding events with orthogonal electrical, optical, or mass sensing label-free readouts. Furthermore, the functionalized glycosylated conductive polymers can be designed and synthesized with controlled oxidation states, desired ionic dopants, and the imperative density and orientation of the sugar ligands that enable the assessment of differential receptor binding profiles of carbohydrate−protein interactions with much more detailed information and high accuracy. Finally, the glycosylated biosensing interfaces were successfully validated for their applications in Gram-negative bacterial detection, antibiotic resistance studies, and antimicrobial susceptibility assays, all based on inferring carbohydrate−protein interactions directly on cell surfaces.
9:00 PM - SM8.10.18
Decrease of Tg of Polymers from Morpholinediones by Modification with Hexyl Groups
Xingzhou Peng 1 2 3 , Marc Behl 1 3 , Pengfei Zhang 1 2 3 , Andreas Lendlein 1 2 3
1 , Institute of Biomaterial Science and Berlin-Brandenburg Centre for Regenerative Therapies, Helmholtz-Zentrum Geesthacht, Teltow, Brandenburg, Germany, 2 Institute of Chemistry, University Potsdam, Potsdam Germany, 3 , Tianjin University-Helmholtz-Zentrum Geesthacht Joint Laboratory for Biomaterials and Regenerative Medicine, Teltow, Brandenburg, Germany
Show AbstractOligodepsipeptides (oDPs), alternating copolymers of α-amino acids and α-hydroxy acids, are typically created by ring-opening polymerization (ROP) of morpholine-2,5-dione derivatives (MDs). In general, oDPs exhibit relatively high glass transition temperatures (Tgs) caused by the strong intermolecular H-bonding between amide and ester bonds [1,2]. Motivated by the need of materials for biomedical applications, which are capable to degrade in a short time period and do not cause a substantial decrease of pH, we explored whether the thermal properties of the oDPs can be adjusted by introducing a hexyl side chain. Our concept aimed at introducing atactic bulky side groups, which hinder hydrogen bridge bonds between the oligomer chain segments. Two novel morpholine diones with an atactic pendant hexyl group, a (3R,S)-hexylmorpholine-2,5-dione (3HMD) and a (3S, 6R,S)-3-methyl-6-hexylmorpholine-2,5-dione (3M6HMD), were synthesized. The synthesis of 3HMD was achieved by reaction of 2-amino octanoic acid, which was derived from 2-bromo-octanoyl chloride, and 2-chloro acetic acid chloride, and the subsequent ring-closing reaction of the 2-[(2-chloroacetyl)amino]octanoic acid. The overall yield was 7% and the identity and purity of 3HMD was shown by NMR spectroscopy and high resolution mass spectrometry. 3HMD had a melting point of Tm = 100±2 °C. 3M6HMD was synthesized by reacting 2-bromo-octanoyl chloride with alanine and subsequent ring-closing of the N-(2-bromo octanoyl) alanine in an overall yield of 15%, 3M6HMD had a Tm = 117±2 °C.
The influence of a modification at the position 3 compared to a modification at position 6 towards ROP was investigated. In contrast to the oligomer obtained from ROP of a MD providing a methyl group at position 3, which had a Tg ≈ 65 °C, in both cases the atactic bulky side groups hindered the H-bonding between chain segments resulting in a significant reduction of the Tgs to a temperature around human body temperature (32 and 36 °C). Such low Tg oDPs could be interesting candidate materials for biomedical applications such as degradable implants [3].
Acknowledgments:
This work was financially supported by the Helmholtz-Association through programme-oriented funding, the Deutsche Forschungsgemeinschaft (DFG) through the Collaborative Research Centre 1112 “Nanocarriers”, subproject A03, the Tianjin University-Helmholtz-Zentrum Geesthacht, Joint Laboratory for Biomaterials and Regenerative Medicine, which is financed by the German Federal Ministry of Education and Research (BMBF, Grant No. 0315496) and the Chinese Ministry of Science and Technology (MOST, 2008DFA51170), and X.P. gratefully acknowledges funding by the China Scholarship Council (CSC) (grant No. 201206250098).
References:
[1] in 't Veld, P. J. A. et al. Makromol. Chem. 1990, 191: 1813 -1825.
[2] Barrer, D. A. et al., Macromolecules 1998, 28: 425-432.
[3] Yancheva, D. et al. J. Molecul. Struct. 2012, 1016: 147–154.
9:00 PM - SM8.10.19
Organic Polyimide—Organometallic Tin Polyester Multicomponent Hybrid as Dielectric Materials
Shamima Nasreen 1 2 , Gregory Treich 1 , Matthew Baczkowski 1 , Mattewos Tefferi 3 , Yang Cao 3 , Gregory Sotzing 1 2
1 Polymer Program, University of Connecticut, Storrs, Connecticut, United States, 2 Department of Chemistry, University of Connecticut, Storrs, Connecticut, United States, 3 Department of Electrical and Computer Engineering, University of Connecticut, Storrs, Connecticut, United States
Show AbstractAdvances in high dielectric constant materials will help in the development of energy storage in capacitors, photovoltaics, photonics and transistors.1 There are many challenges to discover high energy density dielectric materials with low loss for modern energy storage applications. One such challenge is to improve the dielectric constant of the material while maintaining good film quality. Recently enhancement in dielectric constant is achieved by incorporating metal atoms in the polymer chain backbone found to be a promising field due to the improved electrical properties with high dielectric constant with high band gaps2 . Two such organometallic polymers poly (dimethyltin 3,3-dimethylglutarate) (pDMTDMG) and Poly (dimethyltin glutarate) (p(DMTGlu) shown to have promising results in their dielectric properties.3,4 However, there are difficulties in their processing as free standing films. Organic polyimides historically have shown excellent film forming ability with moderate dielectric constants. In this study, organic polyimide and organometallic tin polyester multicomponent hybrid films were made and optimized by blending a polyimide with the organometallic tin polyesters p(DMTDMG) and p(DMTGlu). These hybrid free standing films exhibit dielectric constants close to that of the tin polyesters with values raging from ca. 5.9-6.2, and a low loss ca. 1-2% over a frequency range of 102-106 Hz. These are much higher than the polyimide having a dielectric constant of ca. 3.5. The film quality was further investigated with microscopic techniques to determine the
morphology, while X-Ray Diffraction patterns were used to observe crystallinity of these hybrid films along with the thermal investigations to understand their stability and temperature effect.
References
1. Baldwin, A. F. et al. Effect of incorporating aromatic and chiral groups on the dielectric properties of poly(dimethyltin esters). Macromol. Rapid Commun. 35, 2082–2088 (2014).
2. Mannodi-Kanakkithodi, A. et al. Rational Co-Design of Polymer Dielectrics for Energy Storage. Adv. Mater. Prog. Rep. (2016). doi:10.1002/ adma.201600377
3. A. F. Baldwin, R. Ma, A. Mannodi-Kanakkithodi, T. D. Huan, C. Wang, M. Tefferi, J. E. Marszalek, M. Cakmak, Y. Cao, R. Ramprasad, G. A. Sotzing, Adv. Mater. 2015, 27, 346.
4. G. M. Treich, S. Nasreen, A. Mannodi-Kanakkithodi, R. Ma, M. Tefferi, J. Flynn, Y. Cao, R. Ramprasad, G. A. Sotzing, ACS Appl. Mater. Interfaces 2016, acsami.6b04091
9:00 PM - SM8.10.20
Porous Fe-Mn-HA Biocomposites for Degradable Fracture Fixation Devices
Michael Heiden 1 , Lia Stanciu 1
1 , Purdue University, West Lafayette, Indiana, United States
Show AbstractThe present researchers are investigating the use of resorbable biocomposites such as Fe-Mn-HA to replace more inert fracture fixation implants with nontoxic, transient ones. Different combinations of NaCl-leaching techniques were used to generate a range of controllable porosities, along with incorporating various amounts of hydroxyapatite (an essential and natural mineral in bone) into the material during the sintering process. A separate Ca2Mn7O14 phase formed above 1200C, which was found to encourage cellular attachment, stabilize the matrix to eliminate flaking, and substantially increase degradation rate upon immersion. Mouse bone marrow mesenchymal stem cells (BMSCs) (D1 ORL UVA) were seeded onto the materials and immersed in DMEM for a period of thirty days in vitro. Through the use of MTS assay and fluorescence microscopy it was discovered that porous Fe-30wt%Mn-10wt%HA biocomposites lead to a significant enhancement of D1-UVA cell attachment compared to non-porous Fe-30Mn. Both sample sets: (50wt% NaCl-leached Fe-30%Mn) and (10%HA+30wt% NaCl-leached) with 300 µm diameter pores also showed substantial increases in degradation rates of 0.79±0.05 mm/year and 0.82±0.04 mm/year respectively, compared to 0.02±0.00 mm/year for nonporous Fe30Mn. Results of the effects of these unique bioactive surfaces on bone marrow stromal cell attachment, degradation rate, and mechanical properties will be discussed in-depth.
Symposium Organizers
Andreas Lendlein, Helmholtz-Zentrum Geesthacht
Kevin Cavicchi, University of Akron
LaShanda Korley, Case Western Reserve University
Bernd Rehm, Massey University
Symposium Support
MedShape, Inc.
MilliporeSigma
SM8.11: Advanced Functional Materials II
Session Chairs
Friday AM, April 21, 2017
PCC North, 100 Level, Room 124 A
9:30 AM - SM8.11.01
Superabsorbing Polymers for Breathable and Self-Sealing Smart Hazmat Suits
Kenneth C. Manning 1 , Akshay Phadnis 1 , Timothy Burgin 2 , Konrad Rykaczewski 1
1 , Arizona State University, Tempe, Arizona, United States, 2 , Naval Surface Warfare Center Dahlgren Division, Dahlgren, Virginia, United States
Show AbstractSuperabsorbent polymers are a class of stimuli-sensitive polymers that undergo multifold swelling upon contact with the suitable solvents. These polymers could replace the currently non-permeable hazmat suits with a breathable suit that can swell shut upon contact with hazardous liquids (stimuli). Current hazmat suits provide constant protection by remaining non-permeable at all times, but create an environment where the wearer can easily overheat due to inefficient heat transfer. Breathable suits, using superabsorbent polymers, can adaptively swell preventing permeation of hazardous materials and can allow the wearer to work longer and more comfortably. In this work we have developed a superabsorbent polymer for organic liquids and evaluated its potential for use in smart hazmat suits. The polymer, a non-electrolyte hydrophobic network, swells significantly on contact with multiple organic solvents and could be used to protect against many known chemical threats. The swelling phenomenon of the polymer has been characterized experimentally in terms of swelling ratio, swelling time, and repeatability for selected choice of solvents. A mathematical model has also been implemented in order to describe the swelling behavior of the polymer. This macro-model combines the solvent migration inside the polymer network and deformation mechanics for swelling phenomenon with non-equilibrium thermodynamics. The model has been verified with the experimental results and used to simulate response of a variety of smart hazmat suit geometries to organic aerosol impact.
9:45 AM - *SM8.11.02
3D Printing of Shape-Memory Polymers for Pediatric Medical Devices
David Safranski 1 2
1 , MedShape, Inc., Atlanta, Georgia, United States, 2 , Georgia Institute of Technology, Atlanta, Georgia, United States
Show AbstractShort bowel syndrome is a disorder caused by a lack of sufficient intestinal length that occurs in children at a rate of up to 25 per 100,000 births in the U.S. Without sufficient digestive and absorptive capacity due to the resultant intestinal failure, patients are unable to maintain growth or weight via enteral nutrition and then must rely upon parenteral nutrition, which is associated with a 50% mortality rate. Distraction enterogenesis is an alternative treatment involving the application of mechanical force to increase bowel length and surface area. A solvent-driven shape-memory polymer device has been proposed to achieve distraction enterogenesis. Recently, 3D printers utilizing photopolymerizable urethane systems have enhanced the potential for complex shape-memory polymer pediatric medical devices. The objective is to characterize the shape-memory properties of commercially available 3D printing resin systems and demonstrate novel SMP device designs for distraction enterogenesis.
Test specimens and devices were printed with a M1 printer (Carbon3D) following the manufacturer’s protocol. Thermo-mechanical properties were determined via DMA and monotonic tensile testing. Unconstrained recovery took place at temperatures above Tg and in saline at 37°C. Glass transitions temperatures ranged from 16°C to 135°C for the various resin systems. Rubbery moduli varied from 1.2 to 26.3 MPa. Complete recovery was demonstrated when heated above the glass transition temperature and more than 50% recovery when immersed in saline for 24 hours. Prototype devices were designed for distraction enterogenesis based on radial or axial expansion mechanisms for solvent-driven activation. The results indicate that these resins have the potential to be used for SMP medical devices and activate in vivo. The prototype designs offer multiple methods to achieve distraction enterogenesis for varying anatomical locations.
10:15 AM - SM8.11.03
Fully Biodegradable Shape Change Soft-Gripping Devices
Kunihiko Kobayashi 1 3 , ChangKyu Yoon 2 , Jayson Pagaduan 3 , Seung Hyun Oh 3 , David Gracias 3 2
1 , JSR Corporation, Tokyo Japan, 3 Chemical and Biomolecular Engineering, Johns Hopkins University, Baltimore, Maryland, United States, 2 Materials Science and Engineering, Johns Hopkins University, Baltimore, Maryland, United States
Show AbstractRecently, untethered soft-robotic devices have been developed and utilized for biopsy and drug delivery applications but the materials utilized to make these devices are often not-biodegradable increasing the risk for utilization in humans, especially if they are lost or get left behind in the body. Here, we describe fully biodegradable untethered tiny soft gripping devices composed of poly acrylamide - N,N-Bis(acryloyl)cystamine P(AAm-BAC), poly oligo ethylene glycol methyl ether methacrylate, and bis(2-methacryloyl)oxyethyl disulfide P(OEGMA-DSDMA). We utilized wafer scale patterning to design a variety of shape change microdevices including grippers. These structures fold and bend due to anisotropic differential swelling. Importantly, these devices are fully degraded in the presence of glutathione or similar reducing agents at physiological body temperature (37 °C). Furthermore, as we have verified the devices are non cytotoxic including both before and after degredation. We also show a range of such thermally and magnetically responsive soft drug delivery devices that can move to a desired area, grab targets, release drugs and then be fully biodegraded.
10:30 AM - SM8.11.04
Crosslinkable, Electrospinnable, Biodegradable Polyurethane
Wenbin Kuang 1 2 , Patrick Mather 3
1 , Syracuse Biomaterials Inst, Syracuse, New York, United States, 2 Biomedical and Chemical Engineering, Syracuse University, Syracuse, New York, United States, 3 Chemical Engineering, Bucknell University, Lewisburg, Pennsylvania, United States
Show AbstractWe present the design, synthesis, and characterization of a novel, soft, biodegradable poly(ε-caprolactone) (PCL)-based thermoplastic polyurethane containing unsaturated allyl groups pendent to the backbone. Latent crosslinking to network form can be easily introduced by crosslinking the unsaturation covalently with a thermal initiator, enabling conventional (one-way) and two-way (reversible) shape memory behavior. Importantly, this material allows facile thermal and solvent processing prior to crosslinking, the latter allowing formation of fine, nano-scale fibers via ordinary electrospinning technique. Such processing enables the preparation of unique microstructures and associated of robust shape memory properties. Additionally, with presence of PCL segment, the latent-crosslinkable polyurethanes exhibited desirable biodegradability that depends on the micro- and crystalline structures. Thus, we investigated the effect of processing this material by different means (casting versus electrospinning) on properties before and after crosslinking, respectively. The molecular, thermomechanical and shape memory properties were studied, in particular. In-vitro enzymatic degradation behavior was examined, revealing a dependence on crosslinking state. We envision that this versatile polymeric material will have broad applications in the biomedical field, especially due to latent crosslinking that allows thermal or solvent processing followed by crosslinking.
10:45 AM - SM8.11.05
Shape Memory Polymer Blends
Kevin Cavicchi 1
1 , University of Akron, Akron, Ohio, United States
Show AbstractShape memory polymers are a class of materials which are able to be deformed to a temporary shape and then recovered by the application of an external stimulus, such as heat. A versatile method to prepare shape memory polymers is through the blending of an elastomer and a crystalline small molecule. This method allows the use of commerically available commodity materials, which are synergistically combined to generate responsive materials. Crosslinking of the elastomer generates a permanent network that can be deformed and drives shape recovery, while the crystalline small molecule forms a second, temporary network, that holds the deformed permanent network in place and allows for shape recovery on melting. This talk will focus on shape memory polymers generated from blends of elastomers and crystalline fatty acids. The structure property relationships governing shape memory as a function of the processing conditions (e.g. cold-drawing vs. elevated temperature programming) and the choice of fatty acid.
11:30 AM - SM8.11.06
Reversible Shape-Memory Effect of Crosslinked Thermoplastic Polymer Blends
Muhammad Farhan 1 2 , Karl Kratz 1 , Andreas Lendlein 1 2 3
1 Institute of Biomaterial Science and Berlin-Brandenburg Center for Regenerative Therapies, Helmholtz-Zentrum Geesthach, Teltow Germany, 2 Institute of Chemistry, University of Potsdam, Potsdam Germany, 3 Institute of Chemistry and Biochemistry, Freie Universität Berlin, Berlin Germany
Show AbstractPolymer networks based on crosslinked thermoplastics, having broad melting transitions were recently introduced as actuators exhibiting a reversible shape-memory effect (rSME). Such materials reversibly change their shape upon repetitive heating and cooling, whereby moderate reversible strains below 10% could be obtained [1, 2]. The underlying working principle of these polymeric actuators utilizes lower melting crystallites of the broad melting transition as actuation domains (ADs), while higher melting crystallites act as skeleton forming domains determining the actuators' shape and ensuring the orientation of the ADs. In this study, we explored whether crosslinked blends of poly(ethylene-co-vinylacetate) with a vinyl acetate content of 18 wt% and poly(ε-caprolactone) (cPEVA-PCLs) can provide rbSME with larger reversible strains in the temperature interval between ambient temperature and 70 °C. The number of crystallites in the temperature range of interest, morphology and degree of orientation were considered to have an effect on the reversible shape-memory properties. Two partially overlapping melting transitions with a first peak maximum around 54±1 °C related to the PCL crystals and a second one around 81±1 °C attributed to the polyethylene crystals were observed in dynamic scanning calorimetry experiments for the cPEVA-PCLs. Depending on the composition, droplet in a matrix or co-continuous morphology could be achieved and both phases can be oriented in the direction of applied deformation.A pronounced rSME with reversible strains up to 25% was achieved for all copolymer networks as quantified by cyclic, thermomechanical tensile tests, when repetitively heated to 70 °C and cooled to 25 °C. The obtained large reversible strains of cPEVA-PCLs can be attributed to a higher degree of orientations obtained in such networks.
References [1] M. Behl, K. Kratz, U. Noechel, T. Sauter and A. Lendlein., Temperature memory polymer actuators. PNAS, 2013, 110(31), 12555-12559. [2] M. Farhan, S. R. Chaganti, U. Nochel, K. Kratz and A. Lendlein., Reversible shape-memory properties of surface functionalizable crystallizable crosslinked terpolymer, Polym Advan Technol 2015, 26(12), 1421-1427.
11:45 AM - *SM8.11.07
Artificial Rotary Nanomachines Assembled from Nanoscale Building Blocks
Donglei (Emma) Fan 1
1 , University of Texas at Austin, Austin, Texas, United States
Show AbstractRotary nanomotors, a type of nanoelectromechanical system (NEMS) devices, are critical for advancing NEMS technology in converting electric energy into nanoscale mechanical motions for nanomachines and nanofactories. Traditional fabrication of miniature motors requires complex design and arduous processes and the devices suffer from low yield and short lifetime. It is even more difficult to further reduce the sizes for truly nanoscale motors even with the best available techniques. In this talk, I will discuss our recent progress on innovative design, assembling and operation of new types of rotary NEMS devices made from nanoscale building blocks, such as nanowires and nanodisks. The devices include nanosocillators, rotary nanomotors, nanoscale step-motors, plasmonic-active nanomotors, reconfigurable nanomotors, and bioinspired micromotors. The applications ranging from single-cell drug delivery, analysis to tunable biochemical capture, release, are applied for tunable biochemical release, relevant to research in single cell stimulation, cell-cell communication, and high throughput biosensing.
12:15 PM - SM8.11.08
Synthesis and Characterization of Novel Glucaric Acid-Based Hydrogels
Erik Johnston 1 , Tyler Smith 2 1 , Monica Serban 1
1 , The University of Montana, Missoula, Montana, United States, 2 , Rivertop Renewables, Missoula, Montana, United States
Show AbstractResearch targeting the production and potential uses for glucaric acid has seen increased attention due to a 2004 US Department of Energy report naming it one of twelve "Top Value Added Chemicals from Biomass". Glucaric acid can be produced through a one-step oxidation of glucose and its salt forms are currently being utilized in applications such as water treatment and as sequestering agents. One relatively unexplored area of immense potential for glucaric acid is in the production of biobased, nylon-like polymers. These biodegradable poly(glucaramide)s are of interest due to their ability to form hydrogels at low polymer concentrations. The gels appear to form via a network of polymer nanoparticles which aggregate to create the three-dimensional gel structure when above the minimum gelation concentration, as indicated by scanning electron microscopy and dynamic light scattering. The rheological characterization indicates that the poly(glucaramide) hydrogels are thermoreversible and can gel in a wide range of environments. Based on our findings, we hypothesize that these novel materials could have potential applications as controlled release systems.
12:30 PM - SM8.11.09
Electrically-Induced Shape Change in Patterned Carbon Nanotube-Containing Liquid Crystal Elastomers
Tyler Guin 1 2 , Anesia Auguste 1 , Benjamin Kowalski 1 2 , Vincent Tondiglia 1 2 , Timothy White 1
1 , Air Force Research Labs, Wright Patterson AFB, Ohio, United States, 2 , Azimuth Corporation, Beavercreek, Ohio, United States
Show AbstractLiquid crystal elastomers (LCE) display extraordinary mechanical properties. The local director of LCE films can be spatially patterned in voxels via photoalignment. Here, we report for the first time that the local and hierarchical (through thickness) control of the nematic director can also impart order on nano-inclusions, in this case carbon nanotubes (CNTs). Upon exposure to a DC electric field, these CNT-LCE nanocomposite films constrict anisotropically along the director axis by up to 18%. This response occurs in less than 1 second and increases in magnitude with temperature and voltage. The orientation of the nanotubes was confirmed via Raman spectroscopy, and the alignment of the LCE was confirmed via WAXS and polarized optical microscopy. The oriented CNTs increase the modulus of the film along their orientation direction while still allowing for soft elasticity.
12:45 PM - SM8.11.10
Influence of Metal Softness on the Ring-Opening Polymerization of 2,5-Morpholinediones and Lactones
Axel Neffe 1 , Toufik Naolou 1 , Andreas Lendlein 1
1 , Institute of Biomaterial Science and Berlin-Brandenburg Center for Regenerative Therapies, Helmholtz-Zentrum Geesthacht, Teltow Germany
Show AbstractHydrolytically degradable polymers such as polyesters or polydepsipeptides, i.e. alternating polymers of α-amino and α-hydroxy carboxylic acid, are advantageously synthesized by ring-opening polymerization with an organometallic catalyst via a coordination-insertion mechanism. The efficacy of a catalyst for this reaction is related to the steric crowding of the catalytic center because of metal ligands and substituents on the cyclic monomer, and on the other hand on the efficiency of the chain transfer as well as the suppression of the formation of non-reactive coordinated species. Analyzing the catalytic cycle, we hypothesized that chain transfer and suppression of side reactions according to the Hard and Soft Acids and Bases (HSAB) principle [1] should be promoted by a soft catalyst such as Fe(OAc)2. We compared the activity of this catalyst to the classical Sn(Oct)2 and harder catalysts with low steric demand such as Mg(OEt)2, In(OEt)3, Al(OEt)3 and Fe(OEt)3 [2]. While the metal ethoxides resulted in very limited molar masses and often were connected to partial racemization (Mg, In), or did not catalyze the ROP at all (Al, Fe(OEt)3), here it could be demonstrated that Fe(OAc)2 is very effective for the ROP of s-butylmorpholindione (BMD), giving oligoBMD with a Mn = 5.8 kDa, a narrow polydispersity of 1.1, a conversion ratio of 86 mol%, and no racemization. This catalyst likewise performed well in the polymerization of serine- and tyrosine-based morpholinediones. In the ROP of dilactide with Fe(OAc)2, the addition of the non-polymerizable ethylacetamide did not reduce the efficiency of the polymerization, suggesting that indeed this soft catalyst does not engage into strong interactions with the amide group. A potential benefit of iron catalysts compared to tin catalysts is their lower environmental impact and lower toxicity. The latter was explored in cytotoxicity tests of the synthesized polymers.
References
1. A.E. Martell, R.D. Hancock, Chem. Rev. 1989, 89, 1875–1914.
2. T. Naolou, A. Lendlein, A.T. Neffe, Eur. Polym. J. 2016, published online 10.10.2016, http://dx.doi.org/10.1016/j.eurpolymj.2016.10.011.