Symposium Organizers
Padma Gopalan University of Wisconsin-Madison
Qing Wang The Pennsylvania State University
Hilmar Koerner U. S. Air Force Research Lab/RXBN
Dhandapani Venkatraman University of Massachusetts Amherst
Teruaki Hayakawa Tokyo Institute of Technology
JJ1: Supramolecular Assembly of Hybrid Materials I
Session Chairs
Padma Gopalan
Teruaki Hayakawa
Tuesday PM, November 30, 2010
Independence W (Sheraton)
9:30 AM - JJ1.1
Graphene Oxide as a Polymerization Initiator and as a Carbon Filler in Composites.
Daniel Dreyer 1 , Sun Hwa Lee 3 , Jeffrey Potts 2 , Rodney Ruoff 2 , Sang Ouk Kim 3 , Christopher Bielawski 1
1 Chemistry and Biochemistry, The University of Texas at Austin, Austin, Texas, United States, 3 Materials Science and Engineering, KAIST, Daejeon Korea (the Republic of), 2 Mechanical Engineering, The University of Texas at Austin, Austin, Texas, United States
Show AbstractOwing to their remarkable electronic and mechanical properties, chemically-modified graphenes (CMGs) have emerged as materials of considerable interest. Graphene oxide (GO) often serves as a common precursor to these materials. Possessing a surface rich in various oxygen-containing functional groups (e.g. alcohols, epoxides, carboxylates), GO can be modified with a variety of reagents that bestow upon it desirable properties, such as improved solubility or mechanical properties. We will present a method that employs GO, or functionalized derivatives thereof, as initiators of various polymerization reactions. The resulting composites show good solubility in a variety of organic solvents, as well as improved mechanical/thermal properties and compatibility of the GO with the polymer. Phase separation and aggregation of the carbon can be avoided in this approach to composite preparation.
9:45 AM - JJ1.2
Predicting Nanostructure of Block Copolymer/Nanoparticle Assemblies with a Field Theoretic Approach.
Kahyun Hur 1 , Richard Hennig 1 , Fernando Escobedo 2 , Ulrich Wiesner 1
1 Materials Science and Engineering, Cornell University, Ithaca, New York, United States, 2 School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, New York, United States
Show AbstractBottom-up type assemblies of amphiphilic block copolymers (BCPs) with nanoparticles (NPs) have attracted much attention for the potentially superior properties of the resulting nanocomposite materials for various applications such as electronics, optics, batteries, solar cells, and fuel cells. The use of a BCP as a structure directing agent enables spatial control of the BCP and NP components on the nanometer length scale. However, limited understanding of the underlying physics has hampered progress in this area. Reliable prediction of structure and quantitative analysis of properties by theoretical and simulation approaches may provide helpful insights to key experimental design criteria. In this work, we study BCP/NP self-assembly using a combination of self-consistent field theory (SCFT) and density functional theory (DFT). Long-range Coulomb and hard sphere interactions between NPs were implemented. We found that long-range Coulomb interactions lead NPs to form an ordered lattice within the microphase separated BCP nanostructures. Furthermore, we found that directed ABC tri-BCP assemblies with ligand-stabilized NPs can lead to a chiral NP network structure.
10:00 AM - **JJ1.3
Organic-inorganic Hybrid Copolymers Derived from Silsesquioxane or Carborane Building Blocks.
Edward Coughlin 1
1 Polymer Science, Univ. of Massachusetts, Amherst, Massachusetts, United States
Show AbstractTo explore competitive, or cooperative, effects novel organic-inorganic hybrid copolymers are being prepared and studied. The use of polyhedral oligomeric silsesquioxanes (POSS), a molecularly precise isotropic comonomer, is being utilized to take advantage of the inherent size scale of these particles, average diameters of 1-2 nm. The organic component selected for study in these hybrid systems are either semi-crystalline or amorphous polymers. The architectures of the hybrid copolymers range from random, to precise block copolymers, as well as telechelic and hemi-telechelic end-functionalized model compounds. The degree of POSS aggregation that occurs is found to be a function of thermal history, and processing conditions. Templating, or arresting, aggregation can be achieved using either competitive crystalline organic polymer scaffolds in the bulk, or rapid precipitation. The second inorganic comonomers for study has been constructed from icosahedral carboranes. Dicarbo-closo-¬decaboranes have been widely investigated for their thermal stability, chemical resistance, unique geometry, and the high cross-section for the capture of thermal neutrons. While carboranes have been widely incorporated into small molecules, metal complexes, and on a limited basis in polymer systems relatively little work exists relating their unique properties to systems with extended π-conjugation. Details of the syntheses, characterization and performance properties of both sets of these hybrid systems will be discussed
10:30 AM - JJ1.4
Directed Self-assembly with Density Multiplication of Cage Silsesquioxane-containing Block Copolymer Via Controlled Solvent Annealing.
Hiroshi Yoshida 1 , Yasuhiko Tada 1 2 , Yoshihito Ishida 3 , Tomoyasu Hirai 3 , Joan Bosworth 4 , Elizabeth Dobisz 4 , Ricardo Ruiz 4 , Teruaki Hayakawa 3 , Mikihito Takenaka 2 , Hirokazu Hasegawa 2
1 Materials Reserach Laboratory, Hitachi Ltd., Hitachi Japan, 2 Department of Polymer Chemistry, Graduate School of Engineering, Kyoto University, Kyoto Japan, 3 Department of Organic and Polymeric Materials, Tokyo Institute of Technology, Tokyo Japan, 4 San Jose Research Center, Hitachi Global Storage Technologies, San Jose, California, United States
Show AbstractDirected self-assembly of block copolymers (BCP) stands out as a promising alternative to overcome limitation in conventional lithographic techniques. Extensive work has shown that thermally self-assembled PS-block-PMMA may be aligned to lithographically defined chemical template with density multiplication [1,2]. However, the minimum dimension which can be attained by PS-b-PMMA is limited by its weak segregation power. Here we report density multiplication of chemically patterned template employing a strongly segregating polyhedral oligomeric silsesquioxane (POSS) containing block copolymer for extending the technique to smaller dimensions.The POSS-BCP, polymethylmethacrylate-b-polymethacrylate POSS (PMMA-b-PMAPOSS), and hydroxyl-terminated polymethacrylate POSS (PMAPOSS-OH) were synthesized by living anionic polymerization [3]. Chemical template was prepared by pattering PMAPOSS-OH layer grafted on Si wafer by electron beam lithography. PMMA-b-PMAPOSS which self-assembles into hexagonally closed packed (hcp) array of dots with lattice spacing d=13nm was spin coated on the chemical template with doubled hcp lattice spacing d=26nm, and annealed under controlled CS2 atmosphere. By tuning the swell ratio of PMMA-b-PMAPOSS during annealing, an ordered array of dots with d=13nm, which corresponds to 3.5Tbit/in2, was obtained by interpolating dots in between the chemical template pattern and thus multiplying pattern density of the chemical template in a factor of 4.PMMA-b-PMAPOSS can potentially self-assemble into ordered domains with sub 10nm lattice spacing. The developed process therefore will provide a promising method for extending lithographical capability to very small dimensions for applications, including bit patterned media for next generation hard disk drives [4].[1] R. Ruiz et al., Science 321, 936 (2008).[2] Y. Tada et al., Polymer 50, 4250 (2009).[3] T. Hirai et al., Macromolecules, 41, 4558 (2008).[4] Authors acknowledge Prof. Padma Gopalan, University of Wisconsin-Madison, for supporting the synthesis of PMMA-b-PMAPOSS. This work was supported by New Energy and Industrial Technology Development Organization, Japan.
10:45 AM - JJ1.5
The Origins of Buckle Formation in Vapor Deposited Oxides on Polymers.
Michelle Casper 1 , Ying Liu 2 , Michael Dickey 2 , Kirill Efimenko 2 , Jan Genzer 2 , Jon-Paul Maria 1
1 Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina, United States, 2 Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina, United States
Show AbstractElectronic and photonic materials with periodically patterned micro- and nanostructures are of increasing and substantial importance [1]. Consequent to this interest, spontaneous surface buckling has been transformed from a nuisance associated with hard and soft multilayers to a naturally occurring and attractive opportunity for producing hierarchically corrugated surfaces with intrinsic functionality. We investigate the origins of buckling instabilities in the indium tin oxide (ITO) – polydimethylsiloxane (PDMS) multilayer system and explore strategies for controlling the morphology with the potential for reversibility and tunability. The parameters investigated include deposition pressure, substrate temperature, strain, and energetic bombardment. We first identify the processing window that results in buckling during both radio frequency (RF) and direct current (DC) magnetron sputtering of ITO on thin film and bulk PDMS. Above a threshold deposition pressure, an unbuckled and cracked topography is observed, while below this pressure, a randomly oriented, wrinkled topography exists. Deposition onto heated PDMS results in two superimposed generations of buckles, each with its own characteristic wavelength, λ. Because these generations experience different dependencies on preparation conditions, this suggests different strain mechanisms, i.e., built-in and thermal expansion mismatch induced strain for the smaller and larger generations respectively. Next, we discuss the influence of internal stress accumulation during deposition on buckling by exploring ITO deposition on polystyrene (PS) films on Si. The samples were imaged as a function of temperature by hot stage microscopy to monitor the onset of buckling. In contrast to the PDMS system, buckling is not observed in PS multilayers until a post-deposition heating step above the Tg of PS is performed. In both cases, one generation of buckles occurs at temperatures above Tg and can be attributed to the relaxation of differential thermal expansion strain. For comparison to PDMS multilayers, ITO can be deposited on PS at T>Tg, and under conditions of internal stress accumulation two buckle generations are found. Collectively these observations allow us to identify the origins of stress generation, and thus buckle formation in multilayer structures. Thermal expansion mismatch, as reported by previous authors, is an important contributor, but stress effects can provide a similar influence.
11:30 AM - JJ1.6
Template-free Formation of Non-hexagonal Close Packing Regular Surface Structures Based on Self-assembly of Monodispersed Polymeric Nanoparticles.
Jun Yuan 1 2 , Ting Zhang 2 , Xinlin Tuo 3 , Jun Qian 4
1 Department of Physics, University of York, York United Kingdom, 2 Beijing National Centre for Electron Microscopy, Tsinghua University, Beijing China, 3 Department of Chemical Engineering, Tsinghua University, Beijing China, 4 Department of Electrical and Computer Engineering, University of Illinois at Chicago, Chicago, Illinois, United States
Show AbstractRegular patterned surface structures are vital for many applications such as photonic or plasmonic devices or templates for preparation of other materials as well as nanosphere lithography. Preparation of such nanostructured surfaces is most efficiently carried out by using self-assembly of monodispersied nanoparticles. However, hexagonal close packing structure is most common result while many applications would benefit from a facile method of producing non-close-packing regular structure. Here we report a template-free approach to the formation of millimeter-sized films of (100) (square) facing face-cantered crystalline films (FCC) of colloidal nanoparticles by self-assembly on silicon substrates [1]. We have shown that the formation of these pseudo-square packing surface patterns is related to the shape of the meniscus at the edges of the substrate, where the particles may suffer additional shear force and higher evaporation. Using this understanding, we can influence that the location and size of these nanoparticles thin films with pseudo-square surface arrangement. Using such approach to self-assemble polystyrene-methacrylic core-shell nanospheres into colloidal crystal films with square-like surface arrangement, we can not only demonstrate distinct optical response due to the surface square arrangement, but we can also transform these colloidal films into ordered pore structures by a simple toluene treatment [2]. By detailed analysis, we have demonstrated the importance of local pseudo-square symmetry and compactness of the nanospheres assembly in determining the nature of resulting multiscale ordered pore structures due to selective fusion and dissolution of styrene-rich polymeric components. [1] T. Zhang, X. L. You and J. Yuan (2009) Langmuir, 25(2), pp 820-824[2] T. Zhang, J. Qian, X. L. Tuo and J Yuan (2010) Langmuir, 26(5), pp3690-3694
11:45 AM - JJ1.7
Electrophoretically Enhanced Fluidic Assembly of Nanoparticles.
Asli Sirman 1 , Cihan Yilmaz 1 , Jun Huang 1 , Sivasubramanian Somu 1 , Ahmed Busnaina 1
1 , NSF Nanoscale Science and Engineering Center for High-rate Nanomanufacturing (CHN), Boston, Massachusetts, United States
Show AbstractNanoparticles have generated much interest due to their potential use in devices requiring nanoscale features. Nanoparticles can serve as Raman spectroscopy substrates, photonic crystals, advanced batteries, biosensors and many other applications. The realization of commercial applications, however, depends on the development of rapid and precise assembly placement of nanoparticles. Fluidic directed self-assembly is one approach to achieving a precise assembly on the surfaces. In fluidic assembly, interfacial capillary forces at the liquid-air interface are used to precisely assemble nanoparticles into topographical geometries. However, the assembly duration is long due to the slow particle migration in the suspension toward the substrate (limited by diffusion). Here, we introduce an enhanced fluidic assembly technique for the rapid and precise directed assembly of nanoparticles onto insulating patterned surfaces. In this method, electrophoresis is used to overcome the diffusion limit encountered when using fluidic self assembly. To accomplish electrophoretically enhanced fluidic self-assembly of nanoparticles onto a dielectric film, a conductive film is utilized below the substrate (insulating film) to enable electrophoretic assembly. A DC electric field is applied between a patterned template and a counter electrode during assembly. The particles move towards the template under the influence of a DC electric field increasing the local particle concentration near the patterned template increase the speed of the assembly process by an order of magnitude or higher. Polystyrene Latex nanoparticles (50 nm) are assembled on a PMMA patterned 150 nm thick PECVD grown silicon oxide surface. A 150nm thick gold film, deposited underneath the oxide layer, is connected to the counter electrode providing the required electric field during the assembly process. We have investigated the effect of particle concentration, pulling speed and oxide thickness on the assembly process. The results show that the magnitude of the applied voltage plays a crucial role in achieving precise assembly at high pulling speed. For example, complete assembly using fluidic assembly can only be conducted speeds of 0.5mm/min or lower. However, when electrophoretically enhanced fluidic assembly is used, complete particle assembly can be achieved at speed of 3mm/min using at 3V. The results also indicate that using an electric field the time involved in fluidic assembly process can be reduced from hours to minutes. The results show that this method can yield a fast and high throughput assembly techniques enabling scalable particle assembly process for high-rate manufacturing of nanoscale devices.
12:00 PM - **JJ1.8
Liquid Crystalline Block Copolymer Template Films for Highly Ordered Nanostructured Materials.
Tomokazu Iyoda 1 , Motonori Komura 1
1 Chemical Resources Laboratory, Tokyo Institute of Technology, Yokohama, Kanagawa, Japan
Show AbstractMicrophase-separated nanostructures in block copolymers have fascinated one to understand the correlation between their ordered structures and the polymer structures so far, and now a new wave is surging on them as the self-assembled nanostructures leading to industrial use as the coming engineered plastics. Emphasis should be placed on both high reproducibility and mass production of these ordered nanostructures through self-assembling nanofabrication processes, expected as one of the powerful counterparts of the top-down-type nanofabrication such as lithography and beam processing.We have developed a series of PEO - liquid crystalline (LC) block copolymers which consist of poly(ethylene oxide) (PEO) and polymethacrylate bearing azobenzene mesogen in the side chain and have fabricated hexagonally arranged and normally aligned PEO nanocylinder domain structures in their thin films. Recently, we have prepared more than 100 kinds of the block copolymers with a variety of polymerization degrees of both blocks and mesogens and fabricated their meter-size area thin films on a roll-type PET film substrate by continuous coating with a microgravure. This success satisfies the above requirements applicable to industrial use and also guarantees their high regularity as reliable nanotemplates for structural transcription to and hybridization with various materials such as metal, semiconductors, and so on. One of the topics is to fabricate well-arranged metal nanoparticles arrays by using the nanocylinder structured template films. Both size and periodicity of the nanoparticles array can be controlled independently by choosing appropriate templates, which has never been achieved so far and can be applied for plasmonics engineering. In this talk, our recent results on multi-lateral structural analyses and several topics on transcription and hybridization will be introduced, together with our advanced polymer designs such as photocrosslinkable nanostructured films and region-specific single molecular modification on the micro-phase-separated nanostructures.
12:30 PM - JJ1.9
Dynamic Ordering of Attractive Monolayer Colloidal Crystals.
Kwan Wee Tan 1 , Yaw Koon Koh 2 , Yet-Ming Chiang 3 , Chee Cheong Wong 4
1 Department of Materials Science & Engineering, Cornell University, Ithaca, New York, United States, 2 , DSO National Laboratories, Singapore Singapore, 3 Department of Materials Science & Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 4 School of Materials Science & Engineering, Nanyang Technological University, Singapore Singapore
Show AbstractIonic colloidal crystals, analogue of atomic ionic compounds and stabilized by long-range electrostatic attractions, have the potential to result in a wide diversity of nanostructures for novel photonic and phononic applications. However, electrostatic attractive interactions often result in irreversible coagulations and disorders between the oppositely-charged colloids and substrates. Here we demonstrate particle mobility can be tuned to form well-ordered colloidal crystals using the vertical deposition method even in the presence of electrostatic attractions. We control the ionic strength, colloidal concentration and solvent evaporation temperature to maximize mobility of positively-charged polystyrene particles to order into hexagonal close-packed monolayer colloidal crystals on bare negative glass surfaces. On the same note, the optimization of particulate mobility also allows the crystallinity enhancement of binary two-dimensional superlattices using oppositely-charged colloids grown layer-by-layer.
12:45 PM - JJ1.10
Heterogeneous Hydrothermal Reactions: A New Approach to Self Organized Core-Shell Hybrid Nanostructures.
David Munoz-Rojas 2 1 , Judith Oro-Sole 3 , Pedro Gomez-Romero 2
2 , CIN2, Barcelona Spain, 1 , University of Cambridge, Cambridge United Kingdom, 3 , ICMAB-CSIC, Barcelona Spain
Show AbstractIn the last years there has been a tremendous increase in the number of works involving the synthesis of nanomaterials, an in particular, of tailored nanostructures. The ability to control the final size and shape of such structures is meant to be the cornerstone upon which a new technological revolution is expected to take place. It is therefore a major necessity to fully understand the various processes involved on the nucleation and growth of nanomaterials if we are to achieve such technological breakthrough. Apart from the properties showed by materials at the nanoscale, our incursions in the nanoworld have allowed us to gain knowledge on a fundamental basis on such processes. A clear example is the discovery of Oriented Attachment mechanism, [1] as complementary to the traditional Ostwald ripening mechanism for crystal growth. [2] From the many studies so far performed it is well known that additives and synthetic conditions play a key role on the final structure. Also, and in addition to the peculiar properties associated to nanosized materials, novel properties and functionalities can be achieved by surface modification and combination of different materials. This has yielded a huge amount of mixed and hybrid nanostructures with novel properties.In our group we are exploring new approaches to the synthesis of silver-polypyrrole hybrid nanomaterials. As a result we have developed a simple procedure that yields Ag@Ppy core shell nanostructures.[3] The synthesis involves the use of a suspension of Ag2O in an aqueous Py solution in the absence of any capping agent as PVP or PVA. The hydrothermal treatment of the suspension at temperatures between 120 and 150 C yields the spontaneous formation of novel tortuous Ag@Ppy nanostructures, which have been dubbed “nanosnakes” after their peculiar shapes, which form through self-assembly. Amazingly, the silver cores in these core-shell nanostructures present a high degree of crystallographic coherence in spite of their irregular shapes. In the present work, the experimental conditions for the synthesis of Ag@Ppy nanosnakes, their characterization and a discussion of the formation mechanism will be presented. The shape evolution of such structures and a proposed novel mechanism for crystal growth will also be discussed.[4,5] Finally, the extension of our method to other metals will be explored.[6]1.- a) J. F. Banfield et al., Science 2000, 289, 751. b) R. L. Penn et al., Science 1998, 281, 969.2.- W. Ostwald, Lehrbruck der Allgemeinen Chemie; Vol. 2, Part 1. Leipzig, Germany, 1896.3.- D. Muñoz-Rojas, J. Oró-Solé, O. Ayyad, P. Gómez-Romero, Small 2008, 4, 1301.4.- D. Muñoz-Rojas, J. Oró-Solé, P. Gómez-Romero, J. Phys. Chem. C 2008, 112, 20312.5.- D. Muñoz-Rojas, J. Oró-Solé, P. Gómez-Romero, Chemical Commun. 2009, 5913.
JJ2: Supramolecular Assembly of Hybrid Materials II
Session Chairs
Padma Gopalan
Teruaki Hayakawa
Tuesday PM, November 30, 2010
Independence W (Sheraton)
3:00 PM - JJ2.1
Controlling Hierarchical Self-assembly of Polymer Bristles by Manipulating Meniscus Movement.
Sung Kang 1 , Ning Wu 1 , Joanna Aizenberg 1 2 3
1 School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts, United States, 2 Department of Chemistry and Chemical Biology , Harvard University, Cambridge, Massachusetts, United States, 3 Wyss Institute for Biologically Inspired Engineering, Harvard University, Cambridge, Massachusetts, United States
Show AbstractEvaporation-induced self-organization provides a simple way of assembling ordered and complex structures with different length scales. Previously, by combining top-down and bottom-up approaches, we have demonstrated hierarchical helical patterns of polymer bristles through self-assembly [1]. In this process, controlling nucleation and propagation of the assembled clusters is important for tuning the size and pattern of the resulting assembly. As next steps, we have used various approaches to manipulate the formation and movement of the meniscus for better control of assembly process. In particular, we utilize confined geometries for directing the solvent evaporation and patterning the meniscus movement. We have observed a significant (~50 fold) improvement in the uniformity of the assembled features over large areas. In addition, we have produced intriguingly complex patterns with tunable periodicity and chirality. We will report our work on real-time imaging of the assembly process and mechanistic models for the observed pattern formation. This study enhances our understanding of the self-assembly of polymeric materials for building hierarchical structures and provides a simple way of fabricating complex ordered structures.[1] B. Pokroy, S. H. Kang, L. Mahadevan, and J. Aizenberg, Science 323, 237 (2009).
3:15 PM - JJ2.2
Assembly of Nanoparticles from Bioactive Peptides and Chitosan.
Bing Hu 1
1 Food Science, Rutgers, The State University of New Jersey, New Brunswick, New Jersey, United States
Show Abstract Assembly of nanoparticles from bioactive peptides, caseinophosphopeptides (CPPs) and chitosan (CS) at physiological conditions and various CS/CPPs mass ratios have been systematically studied using a combination of liquid chromatography-tandem mass spectrometry (LC-MS-MS), turbidimetric titration, dynamic light scattering (DLS), electrophoretic mobility (zeta-potential), transmission electron microscopy (TEM), and florescence spectroscopy. Peptides with different amount of clusters of phosphorylated seryl residues have been prepared and identified using LC-MS-MS, which incorporated with CS forming nanoparticles. At low salt concentration, an increase of CS/CPP mass ratio shifted the critical pHφ1, which designated the formation of CS/CPP nanocomplexes, and pHmax, which represented the neutralization of positive and negative charge to higher pH values. The peptide-polymer binding mechanism and the binding constant were analyzed according to the results of DLS, electrophoretic mobility, TEM and florescence spectroscopy. First, negatively charged CPPs interacted with the positively charged CS to form intrapolymer nanocomplexes saturated with CPPs (CPPNP). Then, the negatively charged CPPNP was bridged by added positively charged CS. Finally, novel nano-scaled spherical brushes were formed as additional CS molecule absorbed back to and bound the CPPNP with the number of binding polymers = 1. The binding between the peptides and chitosan was mainly driven by electrostatic and hydrophobic interactions and the polymer-CPPNP binding constant was K=5.4*104 M-1 . Phosphorylated groups and Tryptophan (Tpr) in the CPPs might be the dominant sites for interaction with –NH3+ on the CS molecular chain.
3:30 PM - JJ2.3
Stimuli-responsive Self-assembly of Bionanomaterials toward Reconfigurable Devices.
Yoshiaki Maeda 1 2 , Prerna Kaur 1 , Hiroshi Matsui 1
1 Department of Chemistry and Biochemistry, City University of New York, Hunter College, New York, New York, United States, 2 Department of Biotechnology, Tokyo University of Agriculture and Technology, Koganei, Tokyo, Japan
Show Abstract Stimuli-responsive bionanomaterials have been extensively applied to delivery systems, however recently they are indentified to have a potential to be useful in reconfigurable assemblies in the applications and microelectronics, sensors, and optoelectronics. Our strategy is to design smart building blocks that can response to various stimuli (pH, temperature, light or small molecules) and their attachment and detachment with specific substrates are controlled by molecular recognition, dependent on the stimuli. In this study, we constructed two kinds of stimuli-responsive biomaterials and applied them toward development of reconfigurable devices. One is the reconfigurable system controlled by the interaction between proteins and small molecular ligands. Magnetotactic bacteria synthesize intercellular magnetic nanoparticles, and functional protein can be displayed on the surface of magnetic nanoparticles using gene fusion techniques. Here two protein tags, His6 tag and glutathione S-transferase (GST) tag, were displayed in tandem to play key roles for the reconfigulation. Magnetic nanoparticles displaying His6 tag and GST tag could be attached on the silicon wafer modified with nickel-nitrilotriacetic acid (Ni-NTA) and glutathione respectively. These nanoparticles could be detached from the surfaces by incubating excess imidazole to break the His6 tag –NTA interaction or excess glutathione to break the GST tag-glutathione interaction. This interaction switch could realize the reconfiguration of magnetic nanoparticles on ligand-immobilized surfaces. Light-induced self-assembly (LISA) has potential to be a simpler and more rapid system in the stimuli-responsive smart devices. We genetically developed the building block for the LISA system, a collagen-like triple helix displaying azobenzene-binding peptide (Z877). Azobenzene converts its conformation by UV/Vis irradiation (UV=cis-azobenzene Vis=Trans-azobenzene). Since azobenzene-binding peptide (WPTPPNP) has high affinity toward cis-azobenzene specifically, the photoisomerization could turn on and off the interaction for the switching. After UV irradiation to azobenzene-immobilized wafers at dark room to make cis-rich azobenzene surface, Z877 peptides could bind the substrate due to the high affinity to cis-azobenzene detected by AFM. In contrast few binding was observed on the trans-azobenzene wafer, which was not irradiated by UV. Finally, we applied this LISA system to 3D assembly of gold nanoparticles and Z877 peptide. Recently we discovered that Au NPs can be assembled into 3D superlattices in peptide frames in precise NP arrangement in a large scale production, and here we could reversibly assemble and disassemble the 3D hybrid crystals by conjugating p-aminoazobenzene on NPs after the application of the LISA modulation.
3:45 PM - JJ2.4
Nanomechanical Stimulus by Atomic Force Microscopy Accelerated the Self-assembling Process of Peptide Based Nanofiber.
Jonathan Chang 1 , Xiu-Feng Peng 3 , Joseph Cappello 4 , Hamidreza Ghandehari 2 , Joonil Seog 1
1 Materials Science and Engineering & Bioengineering, University of Maryland, College Park, Maryland, United States, 3 Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio, United States, 4 , Protein Polymer Technologies, Inc., San Diego, California, United States, 2 Pharmaceutics and Pharmaceutical Chemistry and Bioengineering, University of Utah, Salt Lake City, Utah, United States
Show AbstractMany synthetic and natural peptides are known to self-assemble to form various nanostructures such as nanofibers, hollow tubes, or ring-like structures. Environmental conditions such as salt concentration, pH, temperature, protein content, and surface characteristics influence intermolecular interactions, hence the process of the self-assembly. Here we studied self-assembly of a genetically engineered protein polymer composed of silk-like and elastin-like repeats on a mica surface. Silk-elastinlike protein polymers (SELPs) consist of tandem repeats of Gly-Ala-Gly-Ala-Gly-Ser from Bombyx mori (silkworm) and Gly-Val-Gly-Val-Pro from mammalian elastin. At a very low polymer concentration, SELPs readily self-assembled into nanofibrous structures on a mica surface. Examination using atomic force microscopy (AFM) and dynamic light scattering techniques showed that SELPs self-assembled into nanofibers only in the presence of the mica surface but not in the bulk state. Ionic strength had a significant influence on nanofiber growth, indicating the importance of electrostatic interactions between the polymer and the mica surface. Interestingly, SELP with a high content of silk repeat showed very low density of nanofiber initially but the density slowly increased without any addition of SELP from the bulk phase, indicating that the nanofiber grew by self-assembling pre-existing SELP on a mica surface. Furthermore, the rate of fiber growth was dramatically accelerated by mechanical stimulus by AFM. The direction of the newly formed nanofibers was dependent on AFM scanning direction, suggesting that this system is potentially applicable to create nanofiber patterned surface by nanomechanical stimulus.
4:30 PM - JJ2.5
Poly(amino acid)s-mediated Synthesis of Spatially Organized Pt Nanoparticles.
Jae Hyun Jeong 1 , John Haan 1 , Chaenyung Cha 1 , Deryn Chu 2 , Hyunjoon Kong 1
1 Chemical and Biomolecular, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States, 2 , U.S. Army Research Laboratory, Adelphi, Maryland, United States
Show AbstractNanometer-sized noble metal particles are being increasingly studied for use in various applications including photochemistry, electrochemistry, optics, and catalysis. Recently, extensive efforts have been made to improve nanoparticle dispersion to enhance its performance using various surfactants, dendrimers and polyelectrolytes which can tune colloidal interactions. However, it is still challenging to establish a technology in which spatial organization of metal nanoparticles is finely controlled at varied length scales. Here we present that in situ sol-gel polymerization of metal precursors incorporated into self-assembling poly(amino acid) nanostructure would generate metal nanoparticles with regular spacing at the nanometer scale. This hypothesis was examined using poly(amino acid)s substituted with alkyl chains to form various morphologies from a spherical micelle to a bilayer structure. Platinum precursors (K2PtCl4) were mixed with alkyl-substituted poly(amino acid)s solution followed by reduction to activate sol-gel polymerization to form Pt particles. We discovered that particle size and spacing were dependent of the degree of substitution (DS) of alkyl chains. Specifically, alkyl-substituted poly(amino acid)s with DS of 5 % were assembled into a vesicle with an average diameter of 100 nm, and also presented Pt nanoparticles with diameter of 2 to 5 nm exclusively within a bilayer of the vesicle. Furthermore, the resulting Pt nanoparticles showed a significantly enhanced electro-catalytic activity as compared with Pt particles polymerized via bulk sol-gel polymerization. Taken together, the results of this study demonstrated that the size and spacing of metallic particle can be controlled using a self-assembling polymeric template. The resulting particles present strong potentials to significantly improve performance of a variety of energy storage and generation systems.
4:45 PM - JJ2.6
Biomimetic Assembly of Nanoparticles Using Collagen Peptide Framework.
Prerna Kaur 1 , Yoshiaki Maeda 1 , Hiroshi Matsui 1
1 Chemistry, Hunter College, New York, New York, United States
Show AbstractApplying biomimetic strategy to control the self-assembly of complex three-dimensional (3D) architectures could lead to the development of complex device configurations. In order to achieve high yields of ordered macroscopic 3D material, we exploited the specificity and robustness of peptides to design a simple and rapid fabrication protocol that result in high yields of 3D crystals.In this study, we report self-assembly of peptides and ligand-functionalized nanoparticle (NP) into micron scale 3D cube-shaped crystals, creating a physical framework for the proposed biomimetic assembly strategy. Taking advantage of the lateral assembly and robust scaffolding nature of collagen, we designed genetically modified collagen like triple helix peptides as nanowire building blocks that can specifically interact with gold nanoparticles functionalized with streptavidin. The design feature of this triple helix includes a segment of alpha 1 chain of type 1 collagen that displays 15 amino acid based Biotin Acceptor Peptide (BAP)that exhibits effective bio recognition sequence that in vivo biotinylates at specific lysine residue at the N-terminus. Using the intrinsic ability of collagen to self associate, we used streptavidin-functionalized gold nanoparticles that can join the peptide nanowires through the streptavidin-biotin interaction to create cubic unit cells with peptide nanowires forming the framework to align NPs. The high yields that resulted from this simple assembly at various scales predict the ability to create an extensive latticework of cubic microcrystals. The NPs are ordered in a long range with the uniform orientation with high yields of 3D materials in controlled shapes, dependent on the geometry of the NP-peptide lattice. The robust large-scale assembly nature of peptides in ordered structures could be advantageous to generate macroscopic building blocks that still preserve functional nanometric domains in the structure. Altering the size ratio between triple helix peptides and NPs and/or the number of ligands on NPs can alter the final crystalline structure. The ability to synthesize protein based functional hybrid material with peptide assembly and nanoparticles building blocks concurrently provides the functionality derived from both the inorganic fragment for electrical conductivity and the protein fragment for bio catalysis and bio recognition demonstrating the feasibility of using structurally stable protein for the designing novel materials.
5:00 PM - **JJ2.7
Thiol-ene Click Chemistries for the Formation of Nanoparticles and Encapsulation of Bioactive Cargo.
Eva Harth 1 , Alice Van der Ende 1 , Jameson Harrell 1 , Jared Katz 1
1 Chemistry, Vanderbilt University, Nashville , Tennessee, United States
Show AbstractWe report the successful systematic preparation of biodegradable nanoparticles in a variety of distinct nanoscopic size dimensions using the traditional alkyne-azide click chemistry and the thiol-ene click reaction by covalently cross-linking alkyne or allyl functionalized linear polyesters with bisazides or dithiols respectively. Characterization of the particles by dynamic light scattering (DLS), and transmission electron microscopy (TEM) proves that the presented cross-linking chemistries provide novel processes for forming nanoparticles. The mild reaction conditions allow for the encapsulation of bioactive cargo such as peptides and oligonucleotides during nanoparticle formation in organic and hydrophilic media.
5:30 PM - JJ2.8
Examining the Properties of Suspensions and Self Suspended Fluids Based on Cubic Cobalt Oxide Nanoparticles.
Wanda Jones 1 , Lynden Archer 1 , Tamara Smith 2
1 Chemical and Biomolecular Engineering, Cornell University, Ithaca, New York, United States, 2 Chemical Engineering, Tuskegee University, Tuskegee, Alabama, United States
Show AbstractMetal oxide nanoparticles have generated significant scientific and commercial interest in the last decade as platforms for controlling and studying materials chemistry and physics. Cobalt oxide nanostructures, especially the Co3O4 phase, are important materials used for a broad range of electrochemical, magnetic and catalytic applications. Several previous studies have considered synthesis of cobalt oxide nanoparticles and their end-use applications. Fundamental studies of processability and stability of Co3O4 nanostructures are less common, but arguably as important for full exploitation of these materials. In this study we focus on two classes of cube-shaped Co3O4 nanoparticle suspensions. In one group the suspensions are created by dispersing particles in an oligomeric polyethylene oxide liquid carrying predetermined amounts of polyvinylpyrrolidone (PVP) as a capping agent. In the second group, the particles are densely grafted by covalent attachment of an oligo polyethylene oxide (PEG) corona, which also forms the suspending medium. We report on the effect of coupling between the suspending medium and suspended particles on quiescent and shear-induced structural transitions in these suspensions. PEG/PVP-based suspensions show Newtonian behavior under the conditions of this work with shear viscosity as a strong function of particle concentration. Self-suspended fluids exhibit various glassy behaviors as a function of particle concentration.
5:45 PM - JJ2.9
Self-asembling Functionalized Amino Acids into Unusual Shapes.
Justin Barone 1 , Naresh Budhavaram 1 , Kate Harvey 1
1 Biological Systems Engineering, Virginia Tech, Blacksburg, Virginia, United States
Show AbstractMulti-component small molecule systems that are amphiphilic or that can hydrogen bond end-to-end or side-to- side have been shown to self-assemble into a variety of shapes including fibers, rods, sheets, plates, spheres, and tubes. Recently, we have identified a simple route to self-assemble the same shapes from simple one-component systems. The structures form by attaching ethyl vinyl sulfone (EVS) to amino acids in water at pH 9 and room temperature. Choice of amino acid and amount of EVS substitution determines the final shape. Functionalized amino acids spontaneously form structures like fibers, spheres, tubes, and donuts when dried from aqueous solution.
Symposium Organizers
Padma Gopalan University of Wisconsin-Madison
Qing Wang The Pennsylvania State University
Hilmar Koerner U. S. Air Force Research Lab/RXBN
Dhandapani Venkatraman University of Massachusetts Amherst
Teruaki Hayakawa Tokyo Institute of Technology
JJ5: Poster Session
Session Chairs
Wednesday PM, December 01, 2010
Exhibition Hall D (Hynes)
JJ3: Synthesis and Self-assembly of Block Copolymer Materials
Session Chairs
Hilmar Koerner
Dhamdapani Venkataraman
Wednesday PM, December 01, 2010
Independence W (Sheraton)
9:45 AM - JJ3.2
Block Copolymer Nanotiled Electrode for Conducting Polymer Nanostructures.
Hideaki Komiyama 1 , Motonori Komura 1 , Keiji Nagai 1 , Tomokazu Iyoda 1 , Kaori Ito 1 2
1 Chem. Res. Lab., Tokyo Institute of Technology, Yokohama, Kanagawa, Japan, 2 , JST-PRESTO, Kawaguchi, Saitama, Japan
Show Abstract Polymerization for conducting polymers inside the pores of track-etched membrane and anodic porous alumina membrane as a template has been demonstrated to give the nanostructured morphology and tune the properties of the resulting nanostructured conducting polymers due to alignment of the π-conjugated main chains. Electropolymerization for conducting polymers is a well-known technique for providing the thin film and easily controlling the deposited amount. Herein, we demonstrate the electropolymerizaiton for conducting polypyrrole (PPy) using the PEOm-b-PMA(Az)n diblock copolymer thin film as a template, which was developed in our laboratory.1 The PEO nanocylinders of which the diameter and the periodicity are size-tunable with narrow distribution are formed with perpendicular orientation to the substrate in the thin film by microphase-separation. The cylindrical domains are not physical pores unlike the track-etched membranes and anodic porous alumina manbrane. The nanocylinders are filled with PEO in over-cooled liquid state, which exclusively dissolves polar substances such as pyrrole here. The perpendicularly aligned PEO nanocylinder array on an electrode can work as electrochemical nano-scaled electrolytic medium.PEO114-b-PMA(Az)45-coated ITO electrode, Pt plate and Ag/AgCl were employed as working, counter and reference electrodes, respectively. Electropolymerization of pyrrole was performed under potentiostatic or galvanostatic condition. The template was taken off from the top surface by dissolution method with a mixed solution of toluene and acetone under spinning condition, called chemical etching here. AFM and FE-SEM observation gave hexagonal dot-pattern with dot diameter of 10 nm and the periodicity of 27 nm, corresponding to those of the PEO nanocylinder domains. The chemical etching clearly revealed the top edges of PPy nanowire array halfway growing through the PEO nanocylinders. When further electropolymerization was proceeded, the PPy nanowires grew over the template film and then the PPy film was covered over the surface of the template. The length of nanowires was controlled by the film thickness of the template and the amount of passed charge. We have successfully obtained the PPy nanowires up to 1.4 μm in height. We have also fabricated the PPy nanowire array with the size of (diameter-nm, periodicity-nm) = (7, 13) and (17, 35) by using the PEO40-b-PMA(Az)17 and PEO272-b-PMA(Az)94 template, respectively, by adopting various block copolymer templates with different PEO size. The nonporous PEOm-b-PMA(Az)n thin film composed of two kinds of microdomains with chemical contrast can be expected as a nanotiled template. Electropolymerization could be carried out in not only the nanocylindrical microdomains but also in the matrix domains by solubility of monomers, supporting electrolyte and solvent to the microdomains.[1] T. Iyoda et al., Macromolecules 2002, 35, 3739
10:00 AM - **JJ3.3
Self-assembly of Block Copolymers and Applications to Semiconducting and Bioinspired Molecules.
Rachel Segalman 1 2 , Adrianne Rosales 1 2 , Victor Ho 1 2 , Ron Zuckermann 2
1 Chemical Engineering, UC Berkeley, Berkeley, California, United States, 2 Materials Science Division, Lawrence Berkeley National Laboratories, Berkeley, California, United States
Show AbstractThe ability to control nanoscale structure in functional systems such as semiconducting polymers for energy generation or biologically inspired polymers would enable new applications, but control over self-assembly in these systems presents new challenges. In particular, the thermodynamics of self-assembly in these systems is significantly altered from that of well-characterized classical block copolymers due to differences in chain topology and the liquid crystalline and/or crystalline interactions. We have studied both the fundamental self-assembly of molecules of unusual shapes as well as applied these principles to conjugated rod-like blocks for photovoltaic and light emitting devices and to bioinspired polymers with tunable molecular conformations. In both cases, we find that careful molecular design to moderate molecular interactions is essential in creating controllable systems. In particular, both sidechain substitution and sequence control can be used to control melting temperatures and liquid crystalline interactions in order to create a processing window in which self-assembly can occur. The role of intermolecular interactions as well as mechanisms for pattern control will also be discussed.
10:30 AM - JJ3.4
Multi-functional Smart Materials from Hierarchically Ordered Polymeric Systems.
Rajeswari Kasi 1 2 , Suk-kyun Ahn 2 , Yuxiang Zhou 1 , Prashant Deshmukh 1 , Rubinder Kaur Lakhman 2 , Nitin Sharma 1 , Victoria Briand 1
1 Chemistry Department, University of Connecticut, Storrs, Connecticut, United States, 2 Polymer Program, University of Connecticut, Storrs, Connecticut, United States
Show AbstractCholesterol can be used as a building block to prepare main-chain and side-chain liquid crystalline polymers (LCPs) in which the cholesteryl moieties self-assembles into different liquid crystalline (LC) mesophases. These LC mesophases include layered smetic A, C, nematic and cholesteric structures that can be tailored based on the composition of the polymer, presence of functional groups and polymer processing conditions. We wish to exploit the stimuli-responsive properties of these LCPs bearing side-chain cholesteryl moieties towards the creation of multi-functional smart materials. We have synthesized cholesterol bearing liquid crystalline homo-, random and block polymers with additional functional (or polar) groups, composition, and architecture. Our synthetic protocol has been used as a handle to tailor the thermal and morphological properties of these LCPs. We have investigated strategies to direct ordering and packing of meso- and nanostructures originating from these LCPs both in solid state and in solutions. These nanostructured polymers with and without inorganic nanoparticle additives have been used to create shape memory devices, actuators, and multi-stimuli responsive materials.
10:45 AM - JJ3.5
Surface Grafted Conjugated Polymers.
Joseph Peterson 1 , Sarav Jhaveri 1 , Kenneth Carter 1
1 Polymer Science & Engineering, University of Massachusetts-Amherst, Amherst, Massachusetts, United States
Show AbstractSurface tethered conjugated polymers have the potential to impact organic electronics by through precise control of interface structures, chain alignment, charge transport, and other properties. Brush structures may give access to well defined structures that are unattainable through traditional fabrication and patterning techiniques. Viable synthetic strategies are the first step towards the practical study and utilization of conjugated brush-type structures.Conjugated polymers were tethered by functionalizing surfaces with monomer-like functionality. Polyfluorene based polymers were tethered to inorganic surfaces such as silicon and quartz wafers as well as to natural fiber surfaces such as paper or cellulose. The surfaces displayed characteristic properties of the grafted polymers such as fluorescence emission, etc, and were stable to subsequent processing, unlike deposited thin films. The surface grafted polymers may have applications in light emitting devices, solar cells, and polymer batteries.
11:30 AM - JJ3.6
Block Copolymers for Idealized Morphologies in Organic Photovoltaic Active Layers.
Ioan Botiz 1 , Rafael Verduzco 2 , Seth Darling 1
1 Center for Nanoscale Materials, Argonne National Laboratory, Argonne, Illinois, United States, 2 Department of Chemical and Biomolecular Engineering, Rice University, Houston, Texas, United States
Show AbstractBy controlling the nanoscale morphology within organic photovoltaic active layers, there are opportunities to gain insights into structure-property relationships that underlie device performance. Block copolymers, which naturally self-assemble into periodic ordered nanostructures, can be utilized in diverse ways to control morphology, ranging from active layers to structure directors to a combination of these methodologies. We present two such approaches, based on rod-rod and rod-coil block copolymer architectures, respectively. Through structural and spectroscopic studies of ordered donor/acceptor systems, connections between the morphology and the optoelectronic properties are deciphered.
11:45 AM - JJ3.7
Facile Synthesis of Well-defined Coil-rod-coil Block Copolymers Containing Regioregular Poly(3-hexyl thiophene) by Anionic Coupling Reaction.
Hong Chul Moon 1 , Jin Kon Kim 1
1 Chemical Engineering, POSTECH, Pohang, Kyung-buk, Korea (the Republic of)
Show AbstractWe synthesized coil-rod-coil triblock copolymers composed of regioregular poly(3-hexyl thiopene) (P3HT) block via anionic coupling reaction. Two different coil blocks (poly(2-vinyl pyridine) (P2VP) and polyisoprene (PI)) were selected. P2VP-b-P3HT-b-P2VP copolymer was synthesized in a polar solvent of tetrahydrofuran, while PI-b-P3HT-b-PI copolymer was synthesized in a nonpolar solvent of benzene. For the synthesis of both block copolymers, the chain ends of the P3HT were capped by the aldehyde group. When the excess amount of the living P2VP (or PI) anions was used, all of aldehyde-capped P3HT were completely reacted with P2VP (or PI) anions, without leaving any P3HT homopolymer in the product. Neat block copolymers were separated from the crude product by column chromatography, resulting in well-defined sharp and narrow molecular distribution.
12:00 PM - **JJ3.8
Diblock Copoly(3-alkythiophene)s: Synthesis, Self-Assembly and Their Uses in Photovoltaic Cells.
Samson Jenekhe 1 2 , Guoqiang Ren 1 , Pei-Tzu Wu 1 , Raffaele Mezzenga 3
1 Department of Chemical Engineering, University of Washington, Seattle, Washington, United States, 2 Department of Chemistry, University of Washington, Seattle, Washington, United States, 3 Department of Physics and Fribourg Center for Nanomaterials, Fribourg University, Fribourg Switzerland
Show AbstractBlock conjugated copolymers are of growing interest in the fabrication of bulk heterojunction solar cells because of their intrinsic ability to form nanoscale domains by self-assembly. We have synthesized and investigated the solution-phase self-assembly, melt-phase phase behaviour, and optoelectronic properties of new all-conjugated diblock copoly(3-alkylthiophene)s. The morphology, charge transport, and photovoltaic properties of poly(3-butylthiophene)-b-poly(3-octylthiophene) (P3BT-b-P3OT) have been investigated as a function of block composition. Diblock copoly(3-alkylthiophene)s annealed above the homopolymer melt transitions (280 °C) were observed by small and wide angle X-ray scattering (SAXS and WAXS) to be microphase-separated into a lamellar structure with two crystalline domains. The microphase-separated domains were characterized by two distinct interlayer d-spacing values that are associated with the two different blocks respectively. In solution, the diblock copoly(3-alkylthiophene)s self-assembled into crystalline nanowires with widths of 14-16 nm and aspect ratios of up to 350-850. Bulk heterojunction solar cells comprising blends of P3BT-b-P3OT and [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM) were found to have power conversion efficiencies as high as 3.0%, which are substantially enhanced compared to those of the homopolymers made under similar conditions. Our results demonstrate that block conjugated copolymers offer a promising approach to advanced materials with tunable morphology and properties for the development of more efficient polymer solar cells.
12:30 PM - JJ3.9
Towards Optimum Morphology of Polymer Bulk Heterojunction Solar Cells.
Chetan Singh 1 , Michael Sommer 2 , Marcel Himmerlich 1 , Stefan Krischok 1 , Mukundan Thelakkat 3 , Harald Hoppe 1
1 Institute of Physics, TU Ilmenau, Ilmenau Germany, 2 Department of Chemistry, University of Cambridge, Cambridge United Kingdom, 3 Applied Functional Polymers, University of Bayreuth, Bayreuth Germany
Show AbstractWe present an approach for achieving optimum morphology in polymer solar cells utilising blend of self assembling donor-acceptor diblock copolymer (DCB) and homopolymer acceptor. In this way, we managed to control the linear rise in open circuit voltage (Voc) and short circuit current (Isc) in the solar cell structure with increasing acceptor content. In the investigated system, the donor and hole conductor was poly(3-hexylthiophene), P3HT, the acceptor and electron conductor was poly(perylene bisimide acrylate), PPerAcr. The improved performance for optimum morphology is attributed to reduced recombination of charge carriers at the cathode interface due to the surface segregation of the acceptor, as identified by atomic force microscopy and X-ray photoelectron spectroscopy measurements. In an effort to engineer the cathode interface, we were able to successfully control Voc at high values (~ 640 mV) by deliberately introducing an acceptor interlayer at the cathode interface.
12:45 PM - JJ3.10
Selenophene-Thiophene Block Copolymers.
Dwight Seferos 1 , Jon Hollinger 1
1 , University of Toronto, Toronto, Ontario, Canada
Show AbstractSelenophene-thiophene block copolymers were synthesized and studied. The properties of these novel block copolymers are distinct from statistical copolymers prepared from the same monomers with a similar composition. Specifically, block copolymers exhibit broad and red-shifted absorbance features and phase separated nanoscale domains in the solid-state. Scanning transmission electron microscopy and topographic elemental mapping confirms that domains are either rich in selenophene or thiophene, indicating that the blocks of distinct heterocycles preferentially associate with one another in the solid-state. This preference is surprising given the chemical similarities between repeat units. The overall results demonstrate a form a phase separation that is controlled by elemental differences. As a result of phase separation and the ability to concurrently control optical properties, these novel conjugated block copolymers should find utility in a variety of studies and optoelectronics uses.
JJ4: Nanostructured Materials for Energy Related Applications
Session Chairs
Wednesday PM, December 01, 2010
Independence W (Sheraton)
2:30 PM - JJ4.1
Porphyrin Nanoparticles: Diversity Enabled via Synthetic Manipulations.
Suk Joong Lee 1
1 Chemistry, Korea University, Seoul Korea (the Republic of)
Show AbstractOver the past decades, the self-assembly approach has developed into a powerful technique for synthesis of nanostructures. Particularly, porphyrins have become one of the most attractive building blocks for self-assemblies because of the enormous potential that they possess in catalysis, photochemistry, sensing, and as optical devices has made them favorite building blocks in the emerging field of molecular materials. With attractive structural features such as large bulk, rigid planarity, and a highly conjugated framework that can be readily modified with a variety of functional groups, porphyrins can be assembled into supra- and super-structures in a relatively facile manner. Indeed, porphyrin building blocks have been used extensively in the construction of nano-, micro-, and macroscopic structures, including nanomaterials using π-π interactions, electrostatic interactions, and metal coordination with appropriate choice of substituents. However, examples of porphyrin based nano particles with different morphology are quite rare. We are particularly interested in the rational synthesis of porphyrin based unique nano particles showing a variety of morphology by the manipulation of secondary substituents (i.e., substituents that are not directly bonded to the porphyrin ring) to engender van der Waals interactions beyond the immediate porphyrin ring. In this presentation, we like to introduce synthesis and assemblies of nano-objects based on the substituents such as carboxylic acids and pyridines on 5 and 15 positions on porphyrin, and influence of secondary substituents in the process of nano-objects assemblies.
2:45 PM - JJ4.2
Fast and Efficient Spin Spray Layer-by-Layer Assembly of Polymer / Carbon Nanotube Hybrid Thin Films for Electrochemical Systems.
David Kohn 1 , Xiaokai Li 1 , Forrest Gittleson 1 , Mauricio Zurita-Gotor 3 , Jerzy Blawzdziewicz 2 , Andre Taylor 1
1 Chemical Engineering, Yale University, New Haven, Connecticut, United States, 3 Ingenieria Aeroespacial y Mecanica de Fluidos, Universidad de Sevilla, Sevilla Spain, 2 Mechanical Engineering, Yale University, New Haven, Connecticut, United States
Show AbstractLayer-by-layer (LbL) assembly, an elegant bottom-up nanomanufacturing technique, has promising applications in fields as diverse as drug delivery, high-strength materials, and electrochemical systems including batteries, fuel cells and solar cells. The great potential of the technique is its ability to blend disparate materials into hierarchical, self-assembled nanocomposites. However, low throughput and material efficiency continue to make the process prohibitively expensive for industrial applications and hinder basic research. Spin spray LbL (SSLbL) addresses these problems by spraying polyelectrolyte solutions or nanocolloidal suspensions onto a spinning disc in rapid succession. Here we show that SSLbL with in-situ heating can achieve short cycle times (< 18 seconds / bilayer) and increase throughput and material efficiency of LbL for electrochemical applications.We used SSLbL to fabricate thin hybrid polymer/carbon nanotube (CNT) electrodes as a model system towards optimizing electrical conductivity. SSLbL assembled films achieved higher transmittance than traditional LbL films with similar conductivities. For instance, a 20 bilayer SSLbL film (16.3 kOhm / sq sheet resistance) transmitted 90% of light at 550nm while a 6 bilayer LbL film (16.9 kOhm / sq sheet resistance) transmitted 85%. Assembling a 20 bilayer SSLbL film requires 6 minutes, compared to a 6 bilayer LbL film, which requires ~ 4 hours. SSLbL’s thinner bilayers and high throughput allow fabrication and characterization of a large number of samples with tunable thickness and conductivity. We observed that conductivity per bilayer increased until saturation and, to explain this behavior, we developed a theoretical model in which junctions between CNT’s were designated to be the major source of sheet resistance. The composite was simulated as a stack of percolating CNT sheets separated by insulating polymer layers. We will show how this model enables optimization of the thin conductive films and provides guidance for further work on the design of nanostructured, high-performance battery electrodes [1] and fuel cell membrane electrode assemblies [2]. [1] Lee, S. W.; Yabuuchi, N.; Gallant, B. M.; Chen, S.; Kim, B.-S.; Hammond, P. T.; Shao-Horn, Y. Nat Nano 2010, advance online publication. [2] Taylor, A. D.; Michel, M.; Sekol, R. C.; Kizuka, J. M.; Kotov, N. A.; Thompson, L. T. Advanced Functional Materials 2008, 18, (19), 3003-3009.
3:00 PM - **JJ4.3
Nanoscale Templating and Assembly in Dye-sensitized Solar Cells.
Michael Durstock 1 , Giorgio Bazzan 1 , James Deneault 2 , Tae-Sik Kang 2 , Barney Taylor 2
1 , The Air Force Research Lab, Wright-Patterson AFB, Ohio, United States, 2 , UTC, Beavercreek, Ohio, United States
Show AbstractThe development of low-cost, lightweight, and flexible energy harvesting devices are an enabling technology for many different solar power applications. The fabrication of highly efficient power conversion devices are highly dependent on the materials and device structures used to make up the active components. Two factors limiting the performance of organic and nanoparticle-hybrid solar cells are limited spectral response and restricted charge transport. These effects can result from poor light absorption, increased carrier recombination, low electronic charge carrier mobilities, or relatively random thin film morphologies. Our efforts to broaden the spectral response of dye-sensitized solar cells are based on developing a detailed understanding of the assembly of dye molecules on the surface of the mesoporous titania film. By utilizing an interfacial modification technique based on layer-by-layer assembly, nanoparticle surfaces can be functionalized with electronically active species and integrated into device structures. This technique is amenable to developing ‘energy cascade’ device architectures commonly utilized in photosynthetic organisms. Our efforts to develop a detailed understanding of this interfacial structure as well as approaches to fabricate multilayer assembled films for enhanced absorption will be described. In addition, our efforts to develop the materials and fabrication methodologies that result in highly ordered device structures to permit enhanced charge transport will be discussed. These include a nano-templating methodology based on porous anodic alumina in order to fabricate vertically aligned titania nanotubes of controllable shape and size. Structure-property correlations relating nanoscale morphology of the nanotubes to device performance will be discussed. In addition, we will highlight current barriers to improved performance and describe a number of specific approaches being investigated to address these issues.
3:30 PM - JJ4.4
Periodic Titania Nanostructures Using A Block Copolymer Templating Approach.
Devon Shipp 1 , Qin Lou 1 , Pavan Chinthamanipeta 1
1 Chemistry, Clarkson University, Potsdam, New York, United States
Show AbstractFor some time now it has been well recognized that phase separation within block copolymer thin films has significant potential in various fields. One such application is that these thin films can form templates with regular, periodic patterns which can be used to deposit or construct other functionality or features; the block copolymer can be later removed using various methods. Additionally, the development of well-ordered semi-conductor nanostructures, especially of titania (TiO2) for photovoltaic (PV) applications, is currently an area of intense interest. However, there are many barriers to overcome if well-ordered TiO2 nanostructures are to become widely applicable. One reason for the difficult production of well-ordered TiO2 nanostructures is the high reactivity of the crystalline surfaces.In this paper we report the preparation of high density arrays of titania nanostructures on silicon and indium tin oxide (ITO) glass substrates using polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) block copolymer template and titanium(IV) bis(ammonium lactate) dihydroxide (TALH) as the TiO2 precursor. The procedure can exclusively involve solution processing and can be applied to a variety of substrates. The PS-b-P4VP block copolymer forms P4VP cylinders that orientate perpendicular to the substrate and it is these P4VP cylinders that are ultimately where the TiO2 are deposited. Various analytical methods, such as field emission scanning electron microscopy (FE-SEM) atomic force microscopy (AFM) and transmission electron microscopy (TEM), show that well-aligned arrays of titania nanostructures are produced and the block copolymer acts as a template for these nanostructures.
3:45 PM - JJ4.5
Semicrystalline Organometallic Block Copolymer Micelles with Symmetrically Substituted Poly(ferrocenylsilane) Compartments.
Felix Schacher 1 2 , Torben Gaedt 1 , Ian Manners 1
1 School of Chemistry, University of Bristol, Bristol United Kingdom, 2 Institute of Organic and Macromolecular Chemistry, University of Jena, Jena Germany
Show AbstractThe self-assembly of poly(ferrocenylsilane) (PFS) containing block copolymers in solution has been described for a variety of different examples. These include unsymmetrically and symmetrically substituted PFS blocks,[1] the latter typically being semi-crystalline. In these cases, cylindrical micelles were formed where the PFS core was shown to be crystalline. Further addition of PFS block copolymers lead to a controlled extension of the cylindrical micellar cores, resulting in a “supramolecular living polymerization”.[2] In this work, we compare this type of crystallization-driven self-assembly for two different, symmetrically substituted, PFS systems, poly(ferrocenyldimethylsilane) (PFDMS) and poly(ferrocenyldiethylsilane) (PFDES). The main aspects we focus on are their preparation, uniformity, size tunability, and the possibility to control both cylinder length and functionality via controlled homo- and hetero-epitaxy in diluted solution.1. J. Massey, K. Temple, L. Cao, Y. Rharbi, J. Raez, M. Winnik, I. Manners; J. Am. Chem. Soc., 2000, 122, 11577-115842. X. Wang, G. Guerin, H. Wang, Y. Wang, I. Manners, M. Winnik; Science, 2007, 317, 644- 647
4:30 PM - **JJ4.6
Aqua Material: A High-water-content Moldable Hydrogel from Clay and Dendritic Binder.
Takuzo Aida 1
1 Department of Chemistry and Biotechnology, The University of Tokyo, Tokyo Japan
Show AbstractWater is essential for life on earth and considered a symbol of purity. 71% of the surface of our planet is covered by water, and our own body is composed of 65% of this simple but vital molecule. Considering increasing environmental issues, the idea of replacing plastics with water-based materials, so-called hydrogels, seems quite reasonable. Here we report that water and clay (2–5%), upon mixing with very minute amounts of organic components (< 0.2%), quickly form a transparent hydrogel. This material can be molded into shape-persistent freestanding objects owing to its exceptionally high mechanical strength, and instantaneously self-heals completely when destroyed. Furthermore, it preserves biologically active proteins for catalysis. Prior to our discovery, no hydrogels, including conventional ones formed by mixing polymeric cations and anions or polysaccharides and borax, have been reported to possess all these exceptional features. Noteworthy, this material is formed only by non-covalent forces resulting from the specific design of a telechelic dendritic macromolecule with multiple adhesive termini for binding onto clay. Since freshly cut surfaces are adhesive, cut objects can then be fused together to construct more complex architectures. By connecting together several blocks with different enzymatic activities, a certain reaction sequence might be designed. Our hydrogel breaks the preconception that materials that are held together by supramolecular forces and mostly composed of water are weak, and may provide many interesting applications. Wang et al., Nature 2010, 463, 339–343.
5:00 PM - JJ4.7
Thermally Reversible Organogels: Donor-acceptor Assemblies of Bicontinuous Porphyrin-fullerene.
Takashi Sagawa 1 , Hirokuni Jintoku 2 , Richard Weiss 3 , Hirotaka Ihara 2
1 Institute of Advanced Energy, Kyoto University, Uji, Kyoto, Japan, 2 Department of Applied Chemistry and Biochemistry, Kumamoto University, Kumamoto, Kumamoto, Japan, 3 Department of Chemistry, Georgetown University, Washington, District of Columbia, United States
Show AbstractThermally reversible organogels based on highly oriented self-assemblies of zinc tetraphenylporphyrin attached with peripheral long-alkyl chains (viz. didodecylglutamide) and bispyridylfullerene were fabricated through hydrogen-bonding of interamide interaction of alkyl chain parts and coordination bonding between the metal center of zinc and pyridyl groups in cyclohexane-THF mixed solvent. Morphological investigation by SEM and TEM observations revealed that porphyrin-fullerene assembly forms vesicular aggregates ranging from 50 nm to 70 nm of the diameters. Relatively strong emission spectra assigned to zinc tetraphenyl porphyrin were observed at 600 nm and 650 nm. These emission peaks were remarkably quenched by the addition of fullerenes. Almost 3-order larger Stern-Volumer constant was observed in the case of zinc tetraphenylporphyrin attached with peripheral long-alkyl chain and bispyridylfullerene as compared to that of zinc tetraphenylporphyrin without the peripheral long-alkyl chain and pristine fullerene. This result implies that bicontinuous porphyrin-fullerene complex formation within the self-assembly promotes the efficient electron transfer as compared with the case of completely dispersed system composed of zinc tetraphenylporphyrin without the peripheral long-alkyl chain and pristine fullerene. In addition, reversible emission changes of heating (colored pink at 60 degree C)-to-cooling (violet, 10 degree C) were also observed.
5:15 PM - JJ4.8
Phase Behavior of Disk-coil Molecules.
YongJoo Kim 1
1 Materials Science and Endingeering, MIT, Cambrdige, Massachusetts, United States
Show AbstractUsing Monte Carlo simulations, we investigate the self-assembly of disk-coil molecules in the NPT ensemble. By changing the interaction parameters between the disk and the coil portion of the molecules, a full phase diagram of these four phases is constructed. Furthermore, we study the ordering of disks within the crystal phase and we find that the confinement imposed by the mesophase segregation induces stronger order compared to the pure disk case, which was also explicitly simulated. Our results show that by reducing the dimensionality of a system it is possible to induce higher order of the molecules and help orient the disks in the crystal phase. Furthermore, we simulated molecules with additional interaction and obtained interesting additional phases. Our results are relevant for organic photoactive (typically planar) molecules that are functionalized with tails to improve their processability and long-range order in the solid phase.
5:30 PM - JJ4.9
Modular Synthesis of Diblock Copolymers for Functional Polymersomes.
Joshua Katz 1 , Daniel Hammer 1 2 , Jason Burdick 1
1 Department of Bioengineering, University of Pennsylvania, Philadelphia, Pennsylvania, United States, 2 Department of Chemical and Biomolecular Engineering, University of Pennsylvania, Philadelphia, Pennsylvania, United States
Show AbstractPolymersomes, synthetic vesicles assembled from block copolymers, are a relatively new class of self-assembled material that show promise for applications in drug delivery and medical imaging. We have designed a novel route to building amphiphilic polymersome-forming diblock copolymers that allows the insertion of a functional group at the blocks’ junction. Through the use of standard peptide synthesis techniques, an amine-terminated PEG (2 kDa) was coupled to an FMOC-protected amino acid using HBTU. Following FMOC deprotection with piperidine, a second HBTU coupling was performed to a carboxy-terminated PCL (9.5 kDa), yielding a PEG-PCL copolymer containing the desired amino acid at the junction. As two examples of the potential utility of modular synthesis and junction functionality, we inserted 2-nitrophenylalanine (2NPA) and a fluorescein-conjugated lysine (FLys) into the diblock. Vesicles assembled from the PEG-PCL copolymer with 2NPA at the blocks’ junction were sensitive to 365 nm UV light. NMR and gel permeation chromatography confirmed UV-induced rearrangement of the 2NPA and liberation of PEG from the vesicles. Encapsulated biocytin was released over a period of 6 hours upon exposure as detected through a modified fluorescent capture assay. No release was observed from vesicles lacking the 2NPA junction. Imaging of these vesicles before and after exposure via cryo-TEM suggests that following PEG liberation the vesicles undergo a hydrophobic collapse in conjunction with expulsion of the encapsulated contents. FLys-containing membranes exhibited strong membrane-localized fluorescence. Images of micron-sized polymersomes were obtained by confocal microscopy. Fluorescent intensities of vesicles comprised of blends of FLys-functionalized polymer and regular PCL-PEG were analyzed by flow cytometry and the intensity was found to increase with increasing amounts of fluorescent polymer. Additionally, increases in intensity were observed with increases in the forward scatter, which is known to correlate with vesicle size. These data confirm uniform distribution of the fluorophore into vesicle membranes. Finally, 200 nm FLys-containing vesicles were incubated with immature dendritic cells for four hours, after which free vesicles were removed and the cells imaged. The bright fluorescence exhibited by the cells suggests that these vehicles could be a new route to cell labeling.
5:45 PM - JJ4.10
The Coiled-coil Motif: Controlling the Self-assembly of Supramolecular Polymers.
Alexander Kros 1
1 Dept. Soft Matter chemistry, Leiden Institute of Chemistry, Leiden Netherlands
Show AbstractBiological self-assembly is very complex, and results in highly functional materials. In effect, it takes a bottom-up approach using biomolecular building blocks of precisely-defined shapes, sizes, hydrophobicity, and spatial distribution of functionality. Inspired by, and drawing lessons from the self-assembly processes in nature, scientists are learning how to control the balance of many small forces to increase the complexity and functionality of self-assembled nanomaterials. The coiled-coil motif is a multipurpose building block that is commonly found in nature, and has much potential in synthetic biology. This contribution examines the roles that the coiled-coil peptide motif plays in natural self-assembly, and then summarises the advances that this has inspired in using the coiled-coil motif to create functional units, assemblies, and systems.References:H. Robson Marsden and A. Kros*. Coiled coil self-assembly in synthetic-biology space: inspiration and progress. Angewandte Chemie Int. Ed. 2010, 49, 2988-3005.H. Robson-Marsden, J.W. Handgraaf, N.A.J.M. Sommerdijk, A. Kros*. Combining Solid-Phase Peptide Synthesis with Ring Opening Polymerization: Synthesis and Self-Assembly of Poly(γ-benzyl L-glutamate)-block-Coiled Coil Peptide Copolymers, J. Am. Chem. Soc. 2010, 132, 2370–2377.H. Robson Marsden, N.A. Elbers, P.H.H. Bomans, N.A.J.M. Sommerdijk, and A. Kros*. A Reduced SNARE Model for Membrane Fusion. Angewandte Chemie Int. Ed. 2009, 48, 2330–2333.H. Robson Marsden, A.V. Korobko, E.N.M. van Leeuwen, N.A.J.M. Sommerdijk, A. Kros*. Coiled-coil peptide mediated self-assembly of amphiphilic supramolecular polymers. J. Am. Chem. Soc. 2008, 130, 9386–9393.
JJ5: Poster Session
Session Chairs
Thursday AM, December 02, 2010
Exhibition Hall D (Hynes)
9:00 PM - JJ5.1
Perpendicular and Parallel Aligned Oxide Nanowire Arrays by Block Copolymer Templating Processes.
Yongbin Zhao 1 , Tomokazu Iyoda 1
1 , Tokyo Institute of Technology, Yokohama Japan
Show Abstract Controlling orientation of the nanometer-sized objects into arbitrary arrangement at will is important for the fabrication of functional nanostructured materials for use in optical, optoelectronic, and magnetic storage devices1. In the previous work, we found that the orientation of the hexagonal cylinder array in amphiphilic liquid crystalline block copolymer (consisting of poly(ethylene oxide) (PEO) and poly(methacrylate) bearing an azobenzene mesogen in the side chain, denoted PEOm-b-PMA(Az)n) thin films out-of-plane and in-plane was controlled by share force in the polymer solution such as just filtering. In this study, oxide nanorod arrays (such as SiO2, TiO2, etc) were prepared separately with perpendicular and parallel orientation by applying the sol-gel method for the orientation-controlled template films. Furthermore, the length of the silica nanorods could be controlled from several tens to several hundred nanometers by adjusting the immersion time and the thickness of block copolymer films. The diameter of silica nanorods and distance of inter-rods also could be controlled by adjusting the molecular weight of PEO and PMA (Az) segment in block copolymer. Finally, this method provides a new means to prepare other oxide material nanoarrays with highly ordered hexagonal structure by using the BCP film templating process.
9:00 PM - JJ5.10
Sub-10-nm Fabrication Based on Templated Self-assembly of Block Copolymer.
Jae-Byum Chang 1 , Jeong Gon Son 1 , Caroline Ross 1 , Karl Berggren 2
1 Department of Materials Science and Engineering, MIT, Cambridge, Massachusetts, United States, 2 Department of Electrical Engineering and Computer Science, MIT, Cambridge, Massachusetts, United States
Show AbstractTemplated block copolymer self-assembly is attractive for fabricating few-nanometer-scale structures at high throughput. Among several morphologies of block copolymer, the cylindrical morphology is particularly important because it can be used for defining metallization lines in IC circuit fabrication. In our previous work, we used polystyrene-polydimethylsiloxane (PS-PDMS) block copolymer because it possesses a high Flory-Huggins parameter and shows a high etch selectivity between the two blocks. We used PS-PDMS block copolymer with a molecular weight of 45.5kg/mol and a half-pitch of 17.5nm. To template the self-assembly of this block copolymer, we used topographically defined templates of different pitches, and shapes. As a result, we fabricated complex structures such as lines with bends or junctions that can be components of an IC circuit over large area. Because the pitch of the cylindrical morphology block copolymer varies with the 2/3 power of N, the degree of polymerization, a lower molecular-weight block copolymer must be used for making smaller structures.Here, we extend this templating approach to template smaller period structures from a lower-molecular-weight PS-PDMS block copolymer (16kg/mol). Because the half-pitch of this block copolymer is only 9nm, it is possible to make sub-10-nm structures using this block copolymer. To make topographical templates, hydrogen silsesquioxane (HSQ) films were spin-coated to a thickness of 19nm on silicon substrate. Single-pixel dots with different pitches were exposed in an electron-beam lithography tool at 30kV acceleration voltage, and the samples were developed in a high-contrast developer system. After that, the surface of template and substrate were coated by short-chain hydroxy-terminated PDMS homopolymer to attract PDMS blocks in PS-PDMS block copolymers. The PS-PDMS block copolymer solution was spin-coated onto the substrates and annealed in a mixture vapor of toluene and heptane. The PS blocks in PS-PDMS block copolymer were selectively removed by reactive ion etching. As a result, PDMS microdomains oriented along one direction, and the direction changed depending on the pitch of template. Based on polymer theory, we expected that PDMS microdomains would be perfectly aligned in one direction at specific conditions, and it was proved experimentally. To increase the level of control over the self-assembly of the low-molecular-weight block copolymer, we also used smaller templating posts whose diameter and height are less than 10nm. To make such small posts, the spin-coated HSQ film was partially dissolved by methyl isobutyl ketone (MIBK) to decrease its thickness, and then electron-beam lithography was carried out. As a result, we found that the effect of template is weak when the diameter and height of posts are less than minimum values. Using this, we are expecting that it is possible to template more complex structures with a mixture of posts of different height and diameter.
9:00 PM - JJ5.14
Flexible Replication Technique of High-aspect Ratio Nanostructures.
Adriana Szeghalmi 1 2 , Kornelia Sklarek 2 , Michael Helgert 3 , Robert Brunner 4 , Wilfried Erfurth 2 , Mato Knez 2
1 Institute of Physics, Technical University of Chemnitz, Chemnitz Germany, 2 , Max Planck Institute of Microstructure Physics, Halle (Saale) Germany, 3 , Carl Zeiss GmbH, Jena Germany, 4 , University of Applied Sciences Jena, Jena Germany
Show AbstractA flexible, non-destructive and cost effective replication technique for nanostructures is presented. The advantages of the process are: 1) it allows for tailoring structural parameters of the replica (e.g. line width) nearly independent on the structural geometry of the master. 2) it allows for replication of high aspect ratio structures also in polymer materials from solution (especially non curable polymers) like polystyrene and PMMA. 3) it includes an easy separation process, thus preserving the master for repeated use. Linear grating replicas with line widths ranging from 88 to 300 nm are obtained using a single nanostructured master. Nanofibers and complex nanopatterned replicas are achievable. The presented technique and its flexibility show that ALD is a unique tool for the preparation of high efficiency polarizer diffractive optics, photonics, electronics, and catalysts.
9:00 PM - JJ5.16
Metal Nanoparticle/Block Copolymer Assemblies in Thin and Bulk Films.
Hitesh Arora 1 , Zihui Li 2 , Hiroaki Sai 3 , Peter Bai 3 , Marleen Kamperman 3 , Sol Gruner 4 , Ulrich Wiesner 3
1 School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, New York, United States, 2 Department of Chemical and Chemical Biology, Cornell University, Ithaca, New York, United States, 3 Department of Materials Science and Engineering, Cornell University, Ithaca, New York, United States, 4 Department of Physics, Cornell University, Ithaca, New York, United States
Show AbstractNanostructured and porous metals in bulk and thin films are interesting for applications in areas of catalysis, plasmonics and energy storage and conversion. Despite considerable progress in the preparations, such materials remain a challenge often due to the high surface energy of metals. In our previous report, organic-inorganic hybrid bulk materials with high metal loadings were synthesized through ligand-stabilized platinum nanoparticles (Pt NPs) self-assembled with poly (isoprene-block-dimethylaminoethyl methacrylate) (PI-b-PDMAEMA) as a structure directing agents.[1,2] Here, we explore the ternary phase diagram of the system by systematically varying the volume fractions of PI, PDMAEMA and Pt NPs. Besides bulk materials, direct access to nanostructured and porous metal thin films with high nanoparticles loading by spin coating of a mixture of block copolymer and metal NPs is addressed.[3] Thin films are characterized before and after further processing using multiple techniques including conductivity measurements. We expect the methods described here to open new routes to nanostructured and porous materials composed of other metals, mixtures of metals as well as intermetallics. [1] Warren, S. C., Messina, L. C., Slaughter, L. S., Kamperman, M., Zhou, Q., Gruner, S. M., Disalvo, F. J., Wiesner, U., Science, 2008, 320, 1748[2] Li, Z., Sai, H., Warren, S. C.; Kamperman, M., Arora, H., Gruner, S. M., Wiesner, U. Chem. Mater, 2009, 21, 5578[3] Arora, H., Li, Z., Sai, H., Kamperman, M., Wiesner, U. Macromol. Rapid Commun. Accepted
9:00 PM - JJ5.18
Directed Ceramic Assembly by Bio-inspired Block Copolymer.
Chetan Hire 1 , Jennifer Bento 3 , Douglas Adamson 1 2
1 Institute of Materials Science Polymer Program, University of Connecticut, Storrs, Connecticut, United States, 3 , Simmons College, Boston, Massachusetts, United States, 2 Department of Chemistry, University of Connecticut, Storrs, Connecticut, United States
Show AbstractSilica is condensed in nature by a variety of organisms at near neutral pH and low temperatures. One such organism, the marine sponge Tethya aurantia, is composed of silica needles composing 75% by dry weight of its mass. Contained within these needles are several proteins, approximately 70% of which is the protein Silicatein α. Previously, we have shown that a functionalized block copolymer, designed with knowledge of the amino acid residues required for the condensation of tetraethoxysilane (TEOS) by the protein Silicatein α, could function nearly as well as the native protein. This block copolymer contains no amino acids. Instead, it is a block copolymer of hydroxyl functionalized polybutadiene and poly(2-vinyl pyridine). Here we present the use of our mimic to form controlled ceramic structures at several length scales at neutral pH and ambient temperatures. Potential applications of these structures as well as their mechanism of formation will be discussed.
9:00 PM - JJ5.19
Synthesis of Thermo-responsive Fluorinated Star-shaped Polymers by Living Cationic Polymerization.
Tomomi Irita 1 , Katsuhiko Imoto 1 , Takabumi Nagai 1 , Sadahito Aoshima 2
1 , DAIKIN INDUSTRIES, LTD., Settsu, Osaka, Japan, 2 Department of Macromolecular Science, OSAKA UNIVERSITY, Toyonaka, Osaka, Japan
Show AbstractWell-controlled fluorinated star-shaped polymers with oxyethylene units were designed and synthesized by living cationic polymerization. These fluorinated star-shaped polymers were prepared using successive fluorinated initiators to generate fluorinated end-functionalized and hydrophilic segments with oxyethylene. Poly(vinyl ether)s with oxyethylene units are known to be thermo-responsive polymer that exhibit a lower critical solution temperature (LCST) in aqueous solution. These novel fluorine-containing star-shaped polymers with oxyethylene were also thermo-responsive, as expected. In addition, the hetero-fluorinated star-shaped polymers with oxyethylene segments and different fluorine compositions were synthesized with various bifunctional initiators by living cationic polymerization with narrow molecular weight distributions (Mw/Mn=1.23-1.29). GPC curves showed very little, if any, presence of the linear homopolymer precursor. The LCST of this polymer depended on the end group fluorine composition and significant changes in cloud points were observed in water, as confirmed by static light scattering (SLS) measurements. As an example, aqueous solutions the star-shaped polymers without fluorine terminal groups showed no cloud point below up to 60 degree C in aqueous solution. After the fluoro-functionality was incorporated into the terminal groups, the cloud point of the aqueous solutions decreased to almost 20 degree C.
9:00 PM - JJ5.2
Study of the Sintering Conditions on the Performance of Hybrid Solar Cells Comprising Novel Nanocrystalline TiO2 Layers.
Sylvia Paul 1
1 , Universität Potsdam, Potsdam Germany
Show AbstractHybrid solar cells combine an organic with a suitable inorganic semiconductor. In most cases, transparent metal oxides (TMOs) serve as inorganic semiconductors, among which TiO2 is the mostly promising electron acceptor. Besides studies on the well-known Grätzel-cell, the combination of a dense or nanostructured TMO layer with a soluble conjugated polymer has been subject to recent investigations. Hereby, the morphology and surface characteristics of the TiO2-films are of great importance, as they affect the exciton diffusion length and carrier transport properties of the TMO in the inorganic/polymeric hybrid-cell. It is expected that the way of layer preparation has a large impact on these properties.We have systematically studies hybrid solar cells comprising dense TiO2 layers formed by nanocrystalline particles. Using a novel synthetic route, dispersions of particles with ca. 5 nm in size and a high degree of crystallinity have been prepared [1] Deposition of such particles on solid substrates via dip-coating yields rather homogenous layers with a high internal surface. The morphology of these layers were studies by atomic force microscopy (AFM), transmissions electron microscope (TEM), scanning electron microscope (SEM), infrared and Raman spectroscopy. In addition, the photovoltaic properties of hybrid devices comprising either a soluble derivative of PPV or a novel polythiophene-copolymer as the hole-accepting component were investigated for various preparation conditions. In particular, we found that the solar cell performance improves with increasing sintering temperature up to 550°C, followed by a prominent decrease for temperatures above 600°C. These effects are discussed with respect to the structural and transport properties of the differently-prepared nanocrystalline TiO2 layers Fig. 1: SEM picture shows the morphology changing from the TiO2 layer at different sintering temperature.[1]M. Niederberger, M.H. Bartl, G.D. Stucky, Chemistry of Materials 14/10 (2002) 4364.
9:00 PM - JJ5.20
Wrinkle Pattern Formation and Optically Induced Anisotropy in Photosensitive Hybrid Sol Gel Glasses
Mark Andrews 1 , Timothy Gonzalez 1 , Tigran Galstian 2
1 Chemistry, McGill University, Montreal, Quebec, Canada, 2 Physics, Laval University, Quebec, Quebec, Canada
Show AbstractBirefringence is induced in sol-gel derived silica containing covalently bound propylmethacrylate and methacrylic acid chelated zirconia clusters when isotropic glassy films are exposed to polarized light. The first part of the talk describes how polarized eigenmode excitation of optically isotropic thin films of glasses in the presence of a light absorbing photo-initiator leads to induced birefringence in the bulk of the films. The birefringence is detected by mode and polarization state selected guided wave Raman scattering. Anisotropy in the waveguides is strongly indicated by changes in the C-H vibrational modes. Surface anisotropy can be induced by exposing 3-5 micron thick films to normal incidence polarized laser light. In the second part of the presentation we describe how the anisotropy can be “read” by decorating the surface of the film with 4-pentyl-4’-cyanobiphenyl (5CB) liquid crystal. Liquid crystal tilt angle and anchoring energy (polar anchoring coefficient) are found to depend on the composition of the glass and the processing conditions of the films. Because the films are metastable, wrinkle patterns with surprising periodicity form spontaneously when the films are exposed to solvent. We examine how guided wave optical self inscription and nanoindentation studies give insight into wrinkle pattern formation. The implications of these findings for integrated optics and liquid crystal display technologies will be discussed.
9:00 PM - JJ5.22
Layer-by-layer Stacking Method for 3-D Nano Structure Fabrication Using Block Copolymer Self Assembly.
Shinichi Warisawa 1 , Ryosuke Kanameda 1 , Reo Kometani 1 , Sunao Ishihara 1
1 Department of Mechanical Engineering, The University of Tokyo, Tokyo Japan
Show AbstractRecent block copolymer self-assembly researches have demonstrated the potential to form aligned line patterns, periodical sphere structures, and directed line and sphere patterns using chemical and physical templates at nano scale. All of these, however, have only been examined on two-dimensional flat substrates. In this research, we offer the possibility of extending self-assembled structures in out-of-plane direction based on layer-by-layer stacking method using thin film transfer. The thin film transfer that we propose prepares two substrates. One is a substrate on which a block copolymer is coated to form some desired self-assembly structure. The other is a substrate on which a water-soluble polymer coating is followed by a block copolymer coating. The water-soluble polymer acts as releasing of the block copolymer thin film from the substrate. Of these copolymer films, the former is hereinafter referred as a “fixed film”, and the latter as “transferred film”. The next step is to put the substrate of transferred film onto the other substrate, tightly contacting two films together and annealing. The annealing process promotes self-assembly to form structures and also connect two films together. The substrates are immersed in water to dissolve the water-soluble polymer layer, and finally the transferred film is released from the substrate. Both or either one of two films may be annealed before contacting together, which depends on polymer characteristics and desired structures. Repeating the procedure mentioned above can fabricate three-dimensional structures in principle. One of interest issues should be paid attention to how structural behavior around the interfacial surface is like and also how the entire self-assembly morphology is influenced. The block copolymer used in our experiments is PS-b-PMMA (PS:PMMA = 50500:20900) to form vertical and horizontal cylinders (line patterns) of PMMA in a matrix of PS. Polyvinyl alcohol (PVA) is used for a releasing film. The fixed film is annealed to form horizontal cylinders, whereas the transferred film is not annealed before releasing. Two films are faced together, fixed tightly, and immersed into water. Finally, the films are annealed. As a result, it is found by AFM and SEM observation that vertical cylinders are formed in the transferred layer, whereas the horizontal cylinders remain formed in the fixed layer. It suggests that the proposed method succeeds in fabricating different cylinder patterns in different layers. The ability to stack nano structures layer by layer using self-assembly materials opens new possibilities of nano fabrication.
9:00 PM - JJ5.23
Monolithic High-performance Antireflection Polymer Film.
Kiwoon Choi 1 , Sung Ho Park 1 , Han Sup Lee 1
1 Advanced Fiber Engineering, Inha University, Incheon Korea (the Republic of)
Show AbstractMoth eyes have a broadband, omnidirectional antireflection property due to their corneal nipple array structure. The antireflection performance of artificial film with a biomimetic sub-wavelength antireflective structure is sensitively affected by the shape and dimensions of the antireflective structure. For the best performance of artificial antireflection film, there is a need for a theoretical evaluation of how the antireflection properties depend on the structural parameters of the antireflective structure; there is also a need for careful fabrication of the best performing antireflective structures. Here, we demonstrate that the ideal antireflective structures predicted by simulation can be successfully fabricated on a poly(methyl methacrylate) surface. The fabrication involves a vacuum-assisted surface wetting method using a nanoporous aluminum oxide template obtained from a multistep anodization process. We also show that the average total reflectivity from an artificial antireflection film with optimized antireflective structures is 0.64% at a wavelength range of 400 nm to 800 nm. To the best of our knowledge, that result is the best antireflection performance ever reported for transparent polymer antireflection films.
9:00 PM - JJ5.24
Self Consistent Field Theory Modeling for Optimizing Block Copolymer Nanolithography.
Adam Hannon 1 , Rafal Mickiewicz 1 , Alfredo Alexander-Katz 1 , Caroline Ross 1
1 Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show AbstractSelf consistent field theory (SCFT) applied to inhomogeneous block copolymer systems is becoming an essential tool in the development of block copolymer nanolithography, in which block copolymers are templated by chemical or topographical substrate features to form desired structures such as arrays of lines, dots or more complex shapes. SCFT can efficiently compute the equilibrium structures of block copolymers without “a priori” knowledge of the stable morphology, by finding the minimum of the mean-field free energy functional that depends on the local polymer composition. SCFT can calculate the microphase-separated morphology of a block copolymer under a range of boundary conditions, allowing a wide range of template parameters to be explored. In this presentation, we show how SCFT can accurately predict the templated morphologies of thin films of polystyrene-polydimethylsiloxane (PS-PDMS) block copolymers in which the PDMS forms spherical or cylindrical microdomains. The templates consist of oxidized silicon wafers on which oxide posts of period L are patterned using electron-beam lithography. The PDMS spheres or cylinders self-assemble on the post array in an arrangement determined by L/Lo, where Lo = 35 or 40 nm is the equilibrium period of the block copolymer [Science 321 939 2008, Nature Nano. 5 256 2010]. Three dimensional SCFT shows how the polymer interacts with the posts by modeling the posts and substrate as static interaction fields, and gives an excellent agreement with the morphologies determined experimentally by removing the PS block, reproducing the effects of commensurability between the polymer and the template period. The effects of post height, PDMS volume fraction, polymer film thickness, and substrate chemistry were then modeled, predicting for example a transition from spheres to cylinders with increasing volume fraction, or the formation of multiple layers of microdomains with increasing thickness. The modeling also predicts the formation of aperiodic features guided by a template with a designed defect. In addition, the self-assembly of a 17 nm period block copolymer on a topographical pattern consisting of mesas and trenches formed from a 35 nm period block copolymer has been investigated. This system demonstrates the hierarchical formation of 17 nm period features aligned with the 35 nm period template. The goal of the combined templating and self-assembly modeling technique is a general optimization process to find the minimum template required to guide the self-assembly of an arbitrary nanopattern.
9:00 PM - JJ5.25
Process Optimization for Nanocrystalline Cellulose Production from Microcrystalline Cellulose.
Christophe Danumah 1 , Hicham Fenniri 1
1 , National Institute for nanotechnology, Edmonton, Alberta, Canada
Show AbstractNanocrystalline cellulose (NCC) is a new family of nanoparticles, which is natural, renewable, biodegradable and can be produced by acid hydrolysis of the widely available cellulose [1]. The growing interest in NCC is due to their relative low density, low cost, high aspect ratios (typically >30-100), high surface area, unique morphology and mechanical properties (rigid rods with 25-30% strength of carbon nanotubes, stronger than steel) [1-4]. Though this class of novel nanocomposites is expected to capture a new market in transportation, medical and packaging applications, electronics and construction [6, 7], its large scale production still poses a major limitation. This paper describes a straightforward method for optimizing the production of NCC by sulfuric acid hydrolysis of microcrystalline cellulose (MCC). By carefully controlling a number of key parameters, NCC was obtained in high yield (~40%). Transmission electron microscopy showed that the rod-shaped NCC had lengths and widths of about 40-400 nm and 3 to 15 nm, respectively. References1. de Souza, Lima, M.M. and Borsali, R. Macromol. Rapid Commun. 2004, 25, 771-787.2. Habibi, Y.; Goffin, A.-L.; Schiltz, N.; Duquesne, E.; Dubois, P.; Dufresne, A. J. Mater.Chem. 2008, 18, 5002-5010.3. Azizi, Samir, M.A.S.; Alloin, F.; Dufresne, A. Biomacromolecules 2005, 6, 612-626.4. Beck-Candanedo, S.; Roman, M.; Gray, D.G. Biomolecules 2005, 6, 1048-1054.5. http://www.esf.edu/cellulose/6. Polymer Nanocomposites and Their Applications; Sinha Ray, S. and Bousmina, M., Eds. American Scientific Publishers (2006) ISBN: 158883-099-3, 600p.7. Hubbe, M.A.; Rojas, O.J.; Lucia, L.A. Sain, M. BioResources 2008, 3(3), 929-980.
9:00 PM - JJ5.26
Graphitic Nanoparticles from Asphaltenes.
Christophe Danumah 1 , Andrew Myles 1 , Hicham Fenniri 1
1 , National Institute for nanotechnology, Edmonton, Alberta, Canada
Show AbstractCarbon materials are of great interest due to their high surface area, large pore volume, high conductivity [1], mechanical strength and thermal properties [2].Much research efforts done in this area have dealt with the development of facile synthesis routes that avoid the use of expensive carbon stocks and/or harsh non-scalable conditions [3, 4]. For example, more recently, inexpensive carbon sources such as candle soot [5], natural gas soot [6], sawdust [3] and biomass processed through hydrothermal carbonization [4] have been used for generating carbon nanomaterials. Asphaltenes have also been investigated in this regard and carbon nanoparticles were successfully generated using electron beam irradiation [7] and chemical vapor deposition [8]. Nonetheless, low production cost and scalability are required for industrial applications. This paper describes a simple strategy for fabricating carbon nanoparticles through careful thermal processing of oilsands by-products (asphaltenes). The resulting carbon nanomaterials of ~20 nm in size, were characterized by SEM, TEM, TGA, XPS, and AES.References1. Prasad, K. E.; Das, B.; Maitra, U.; Ramamurty, U.; Rao, C. N. R. Proc. Nat. Acad. Sci 2009, 106, 13186-13189. 2. Li, H.; Xu, C.; Srivastava, N.; Banerjee, K. IEEE Trans. Elect. Dev. 2009, 56, 1799-1821.3. Sevilla, M.; Sanchis, C.; Valdes-Solis, T.; Morallon, E.; Fuertes, A. B. J. Phys. Chem. C 2007, 111, 9749-9756.4. Titirici, M.-M.; Antonietti, M. Chem. Soc. Rev. 2010, 39, 103-116.5. Liu, H.; Ye, T.; Mao, C. Angew. Chem. Int. Ed. 2007, 46, 6473-6475.6. Tian, L.; Ghosh, D.; Chen, W.; Pradhan, S.; Chang, X.; Chen, S. Chem. Mater. 2009, 21, 2803-2809.7. Camacho-Bragado, G. A.; Santiago, P.; Marin-Almazo, M.; Espinosa, M.; Romero, E. T.; Murgich, J.; Lugo, V. R.; Lozada-Cassou, M.; Jose-Yacaman, M. Carbon 2002, 40, 2761-2766.8. Wang, X.; Guo, J.; Yang, X.; Xu, B. Mater. Chem. Phys. 2009, 113, 821-823.
9:00 PM - JJ5.27
Combinations of 3D Direct Write and Large Area Patterning Techniques for Rapid Fabrication of Hierarchical and Complex Structures.
Jonathan Singer 1 2 , Jae-Hwang Lee 1 2 , Sisi Ni 1 2 , Michael Gibson 1 2 , Steven Kooi 2 , Edwin Thomas 1 2
1 Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 2 Institute for Soldier Nanotechnologies, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show AbstractFor the next generation of photonic, plasmonic, and electronic devices, the capability to create 3D structures is highly desirable. Fabrication of such structures by conventional top-down techniques generally requires many layer-by-layer steps. Large area patterning techniques such as interference lithography or self-assembly provide 3D nanoscale structures, but lack arbitrary control over what regions are patterned. 3D direct write (DW) lithographic techniques such as multiphoton lithography (MPL) possess the capability to fabricate nearly arbitrary patterns; however, due to the serial nature of DW, fabrication is slow relative to other forms of lithography.We have explored a variety of strategies to increase the speed and capabilities of DW by combining it with wider area 3D techniques to create hierarchical structures with fine nanoscale features defined by the large area technique and a superstructure defined by the 3D DW. In this way, both periodic and complex predefined structures may be patterned with nearly arbitrary positioning. For example, we have fabricated arrays of resonant structures with positioning and features defined by a combination of DW and proximity nanoprint phase masking. To best approach these novel technique combinations, we have incorporated a combination of simulation and experiment to determine possible technique combinations and pattern geometries, and further, the properties of the fabricated structures.
9:00 PM - JJ5.28
Highly Tunable Morphology of Silica Nanostructures Synthesized with Self-assembled Siloxane Block Copolymers.
Jae-won Jeong 1 , Yeon Sik Jung 1
1 Material science and engineering, Korea Advanced Institute of Science and Technology, Daejeon Korea (the Republic of)
Show AbstractSilica nanostructures are of great interests especially for biological and optical applications. We introduce a novel, convenient technique to synthesize monodisperse silica nanospheres or nanowires using silicon-containing block copolymers (BCPs). By utilizing the self-assembly of BCPs, ordered arrays of sub-20 nm scale features can be produced for various kinds of applications such as nanolithography or photonic crystals. However, since the volume fraction and chain length of each block are the dominating factors that determine the self-assembled morphologies and domain sizes, the geometry and length scale are, in general, limited by the fixed molecular weight of BCPs. We have developed a practical strategy for enhancing the tunability in dimension and morphology by changing the solvent-treatment conditions of BCPs. Si-containing poly(styrene-b-dimethylsiloxane) (PS-PDMS) with a large Flory-Huggins interaction parameter (χ) was dissolved in various kinds of solvents such as hexane, heptane, dodecane, cyclohexane, xylene, toluene, methyl ethyl ketone, acetone, and pentanol, which are selective for one of the two polymer blocks due to the matching of solubility parameters. The solutions were drop-cast on a substrate and slowly dried for self-organization, and then the dry polymers were thermally treated at 500 – 700 °C in oxidizing atmosphere to remove organic components and generate silica nanostructures. In order to investigate the influences of solvents on the shape and size of the silica nanostructures, the samples were analyzed with scanning electron microscopy (SEM), transmission electron microscopy (TEM) and small-angle X-ray scattering (SAXS). The effect of different solvents was remarkable and twofold. First, by choosing different solvents, the morphology of silica nanostructures can easily be controlled. For example, a cylindrical structure found in the samples prepared with the PS-selective solvents can be converted into a gyroid or less organized morphologies when PDMS-selective solvents are used. A similar morphological conversion between spheres and cylinders was observed as well. These results indicate that the effective volume fraction of each polymer block can be controlled by selectively incorporating solvent molecules into one of the two blocks. Second, the diameter of the silica nanostructures was smaller in the case of a better solvent (e.g. toluene) and larger for a less good solvent (e.g. acetone). Moreover, the solvent drying speed greatly affected the microdomain size of the BCPs. These phenomena can be understood from the change of effective χ-parameter by the different solvent treatment conditions. The effective χ value decreases lineally with the amount of solvent uptake due to a screening effect at the interface between two polymer blocks. The overall influences of solvent quality and drying rate on the morphology and length scale of the generated silica nanostructures will be discussed.
9:00 PM - JJ5.29
Modeling of SEBS Structures during Pattern Dynamic Formation.
Andrea Bianchi 1 , Michele Salvador 1 , Antonio de Carvalho 3 , Marcelo da Silva 2 , Roberto Faria 2
1 Physics Department, University Federal de Ouro Preto, Ouro Preto, Minas Gerais, Brazil, 3 Department of Material Engineering, University of São Paulo, São Carlos, São Paulo, Brazil, 2 Physics Department, University of São Paulo, São Carlos, São Paulo, Brazil
Show AbstractBlock copolymer (BC) pattern structures, in submicrometric scales, resulting from dewetting and solvent evaporation phenomena of thin films, belong to a rich scientific subject related to micro fluidics and BC phase segregation. In bulk, usually phase separation can be observed, due to repulsive interaction between the constitutive block chains. The SEBS thin films arouse interest in lithographic process owing to the micro and nanometric self-organized structures formation. Despite the progress observed in the last ten years towards the understanding of the dynamic formation of block copolymers patterns, our knowledge about the involved phenomena is not completely understood. In such the morphology measurements extraction during the process of film formation should provide contributions to its dynamic of self-organized copolymers. In this work we investigate atomic force microscopy (AFM) images of poly(styrene)-b-poly(ethene-co-butene-1)-b-poly(styrene) (SEBS) deposited over mica substrates by dip coating, and with the help of computational techniques, we developed an explanation for the final part of the pattern formation, i.e. structural dynamics related to the stripes fragmentation. The first step is the structures segmentation, by applying an adaptive threshold algorithm to AFM images of triblock copolymer, different morphological structures have been separated from background. Pattern recognition and labeling of various disjoint and connected components in an image are decisive to reliable automated image analysis, such as, mean area, width and height. First, the Marangoni effect occurs in the vicinity of the contact line during the dewetting of the thin film liquid (still a film in solution), an effect that can be generated by a local gradient of the solute (SEBS molecules) with the contribution of the solvent evaporation. In a second step, the undulations along the contact line triggers the formation of fingers, and as the film shrinks these fingers are stuck in a parallel arrangement on the mica surface composing the pattern of stripes. The third step, which is the main contribution of this work, is related to a particular sort of Rayleigh instability, in which the stripes break up in droplets. It is also known that in thin films of SEBS and similar copolymers the phase separation forms a cylindrical domain structure, and for thin films the cylinders can be oriented in parallel to the solid surface. The model proposes different morphologies of stripes and droplets structures, in which the only difference is in the number of terraces formed by PS-cylinders. Computational image processing was essential to elaborate the model because provided accurate quantitative values for the heights of stripes and droplets, as well as the height variation in transition regions that showed the stripe fragmentation into droplets.
9:00 PM - JJ5.3
Phase Orientation Studies on Block Copolymer Films Confined by Tunable Surface Energy Elastomeric Films and Xerogel Substrates.
Alamgir Karim 1 , Manish Kulkarni 1
1 Department of Polymer Engineering, University of Akron, Akron, Ohio, United States
Show AbstractA novel use of flexible elastomeric PDMS films to control orientation of micro-phase separated Poly(styrene)-block-poly(methylmethacrylate) (PS-PMMA) cylindrical films is presented. Orientation control of block copolymer (BCP) films is important from advanced technological applications like organic photo voltaic devices and nanoscale lithography. Surface energy of crosslinked PDMS films was tuned by exposing the films to UV-Ozone (UVO). The BCP films were then sandwiched between surface energy tunable silica xerogel and silane monolayer coated substrates and conformally contacting crosslinked PDMS elastomer during annealing. This dual tuning of interfacial energies of the top and bottom substrates led to change in orientation morphology of BCP films from parallel, perpendicular or mixed states. The advantage of using a flexible PDMS top layer for confining BCP is that after annealing, the PDMS film was easily delaminated from the top glassy BCP film surface without disturbing the surface morphology. The morphology of these micro-phase separated BCP films was studied using phase imaging by tapping mode atomic force microscopy (AFM) and neutron reflectivity (NR).
9:00 PM - JJ5.30
Color Tuning of Block Copolymer Photonic Gels via Clicking Counterions.
Ho Sun Lim 1 , Jae-Hwang Lee 1 , Joseph Walish 1 , Edwin Thomas 1
1 Materials Science and Engineering, Institute for Soldier Nanotechnologies, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show AbstractBlock copolymers (BCPs) have been used as materials for creating various 1D, 2D and 3D photonic crystals due to their ability to self-assemble into long range ordered microstructures. In particular, their periodic dielectric structures can prohibit the propagation of electromagnetic waves, producing strong reflective colors. Additionally stimulus-responsive BCPs can exhibit variable colors. Here we demonstarte full color tenability for a 1D photonic lamellar gel made of a hydrophobic block-hydrophilic polyelectrolyte block copolymer by proper selection of counterions. The selective swelling of the block copolymer lamellar structure leads to extremely large tunability of the photonic stop band from blue to red wavelengths as a result of direct counterion exchange. The reversible color changes are strongly dependent on the hydration characteristics of the counteranions in the lamellar microdomains. Their colors are also significantly tuned with the ionizing degree of polyelectrolyte block. Based on transfer matrix simulation of the experimental reflectivity data, the photonic gels with more hydrophilic counterions can swell in water by a factor of 9X greater than the original domain size.
9:00 PM - JJ5.31
Interfacially Modified Diblock and Triblock Copolymers using a Combination of Anionic Polymerization and Atom Transfer Radical Polymerization (ATRP).
Jong Keun Park 1 , Raghunath Roy 1 , Sarah Mastroianni 1 , Maeva Tureau 1 , Thomas Epps 1
1 Chemical Engineering, University of Delaware, Newark, Delaware, United States
Show AbstractWe present a strategy that produces tapered diblock and triblock copolymers of poly(isoprene-b-isoprene/styrene-b-styrene) [P(I-IS-S)] and poly(isoprene-b-isoprene/styrene-b-styrene-b-styrene/methyl methacrylate-b-methyl methacrylate) [P(I-IS-S-SM-M)] using a combination of anionic polymerization and atom transfer radical polymerization (ATRP). Our tapered block copolymers with tapers comprising 30 volume percent of the total polymer were shown to exhibit network morphologies as shown through a combination of small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM). The composition of the tapered diblock copolymer lies within the expected gyroid-forming region for conventional poly(isoprene-b-styrene) P[I-S] copolymers, while the composition of the tapered triblock copolymer lies within the triblock network-forming region as determined by non-tapered triblock studies in the ISM system. These results indicate that it is possible to manipulate the composition profile of segments between pure blocks in diblock and triblock copolymers, decoupling polymer interfacial interactions from molecular weight and chemical constituents, while still maintaining the ability to form complex network structures. Though initial experiments are performed on a model system, the copolymer blocks could be chosen specifically for their potential as nano-templates and membrane precursors.
9:00 PM - JJ5.32
Self-assembly of oligothiophenecarboxylic acid monolayer by Scanning Tunneling Microscope (STM)
Chaoying Fu 1 , Oleksandr Ivasenko 1 , Jennifer Macleod 2 , Tyler Taerum 1 , Dmitrii Perepichka 1 , Federico Rosei 2
1 Chemistry, McGill University, Montreal, Quebec, Canada, 2 , INRS-ÉMT, Université du Québec, Montreal, Quebec, Canada
Show AbstractScanning tunneling microscopy (STM) of monolayers comprising oligothiophene and fullerene molecular semiconductors reveals details of their molecular-scale phase separation and ordering with potential implications for the design of organic electronic devices, in particular future bulk heterojunction solar cells. Oligothiophenecarboxylic acid (TTBTA and TTATA) self-assembles at the solution/graphite interface into either a porous network linked by dimeric hydrogen bonding associations of COOH groups (R (8)) or a close-packed network linked in a novel hexameric (R (24)) or tetrameric(R (12)) hydrogen binding motifs. Analysis of high-resolution STM images shows that the pore cavities can efficiently host C60 molecules, which form ordered domains with number of fullerenes per cavity varying from one to four. The observed monodisperse filling and long-range co-alignment of fullerenes is described in terms of a combination of an electrostatic effect and the commensurability between the graphite and molecular network, which leads to differentiation of otherwise identical adsorption sites in the pores.
9:00 PM - JJ5.34
Shifting of the Melting Point for Semi-crystalline Polymer Fibers.
Ying Liu 1 , Shuang Chen 1 , Miriam Rafailovich 1 , Eyal Zussman 2 , Arkadii Arinstein 2
1 Materials Science and Engineering, SUNY at Stony Brook, Stony Brook, New York, United States, 2 Mechanical Engineering, Technion-Israel Institute of Technology, Haifa Israel
Show AbstractElectrospinning of polymeric fibers has been attracted increased interested in recent years. However, the research for semicrystalline polymer, such as polyethylene is still absent, due to their relatively poor solubility in conventional solvent systems at ambient temperature. In this study, poly (ethylene-co-vinyl acetate) (PEVA) and low density polyethylene (LDPE) were electrospun with fiber diameter of several hundred nanometers to tens of microns when the electrospinning solution was kept at a temperature greater than that of the solidification temperature of the polymer solutions. The effects of the fiber physical dimension to its crystallization and mechanical properties were thus detected. The morphology of the fibers was measured, and the melting point was found to increase with increased fiber diameter and crystallinity. Atomic force microscope (AFM) three-point bending test demonstrated that the Young’s modulus of the fibers drastically increased as fiber diameter decreased. X-ray scattering showed that, compared to the bulk material, the crystallinity of the electrospun fibers had changed.
9:00 PM - JJ5.35
Fluorophores and Quantum Dots in Nanostructures of Functional Diblock Copolymers.
Seungyong Chae 1 , Sehee Kim 2 , Yirang Lim 1 , Byeong-Hyeok Sohn 1 2
1 Department of Chemistry, Seoul National University, Seoul Korea (the Republic of), 2 NANO Systems Institute, Seoul National University, Seoul Korea (the Republic of)
Show AbstractQuantum dots have attracted considerable attention due to the unique features such as high resistance to photo bleaching and broad absorption, narrow emission spectra, high luminescence efficiency in the solid state and tunability over a wide emission wavelength range. To apply quantum dot to device fabrication, it should be uniformly dispersed into the matrix materials. Polymers are one of the widely used materials for matrices due to their easy processability. Diblock copolymers are considered as desirable matrix materials because they spontaneously form nanostructures such as spheres, cylinders, and lamellae, which can be used to incorporate quantum dots, via self-assembly. The size and morphology of diblock copolymers can easily be regulated by modifying the molecular weight and volume fraction of copolymers. The arrangement of incorporated quantum dots thus can be manipulated by controlling the nanostructures of diblock copolymers. Nanoparticles, including quantum dots, however, tend to aggregate each other due to their inherently large surface-to-volume ratios. To overcome this problem, the surface of nanoparticles and/or polymeric matrices need to be modified to have preferential enthalpic interaction. In this presentation, we demonstrate hybrid nanostructures of lamellar-forming diblock copolymers and quantum dots. Reactive polymers based on the activated esters, which can be further converted to thiol containing amide groups, were utilized to encapsulate quantum dots. We synthesized Poly(methyl methacrylate)-b-poly(pentafluorophenyl methacrylate), PMMA-b-PFMA by the reversible addition fragmentation chain transfer (RAFT) polymerization. The thiol groups were introduced to PFMA blocks to encapsulate quantum dots by substituting the oleic acid on the quantum dot surface. The PFMA-encapsulated quantum dots were then blended with the pristine PMMA-b-PFMA block copolymers to fabricate the hybrid film of quantum dots and block copolymers. The nanostructures of quantum dot and block copolymer hybrid films were investigated by transmission electron microscope. The PFMA encapsulated quantum dots were well dispersed into the lamellar nanostructures of PMMA-b-PFMA and selectively arranged in the PFMA domains. The optical properties of quantum dots were well preserved after the hybridization with block copolymers, which were measured with UV-vis spectroscopy and photoluminescence spectroscopy. Furthermore, additional fluorophores besides quantum dots could be simultaneously incorporated to the either PMMA or PFMA domains thus the distance between each fluorophores were controlled. The optical properties of fluorophores embedded in the block copolymer films were highly dependent on the arrangement of each fluorophore(i.e. dyes and quantum dots) within the respective domains of the block copolymers.
9:00 PM - JJ5.36
Crystal Nanostructuring in Isotactic Polypropylene-carbon Nanotubes Films.
Georgi Georgiev 2 1 , Scott Schoen 1 , Devin Ivy 1 , Lauren Wielgus 1 , Yaniel Cabrera 1 , Peggy Cebe 1
2 Natural Sicences, Assumption College, Worcester, Massachusetts, United States, 1 Physics and Astronomy, Tufts University, Medford, Massachusetts, United States
Show AbstractWhen carbon nanotubes are introduced in isotactic polypropylene (iPP) materials the iPP crystals assemble in a fibrillar instead of spherulitic arrangement. We study the effects of concentration and isothermal vs nonisothermal treatments on the rate of crystal formation. Those nanocomposites provide means of controlling the crystal orientation in polymer materials by aligning the nanotubes and creating materials with novel properties. We used Differential Scanning Calorimetry (DSC) as our primary method of investigation due to its ability to give detailed data on the phase transitions of iPP nanocomposites with low concentrations of CNTs (0%-5%). We analyzed the crystallization of each sample in the DSC at a range of cooling rates (10-20°C/minute). We found that increased concentrations of CNTs speed up the nanocomposites’ crystallization and decrease the crystal size distribution. The authors thank for research support: Assumption College for Faculty Development Grant and funding for students’ stipends, instrumentation and supplies. The NSF Polymers Program of the DMR, grant (DMR-0602473), NASA grant (NAG8-1167) and the MRI Program under DMR-0520655 for thermal analysis instrumentation.
9:00 PM - JJ5.37
Evaluating the Physical Properties of Zinc Oxide- Polyaniline Nanocomposite Films for Energy Application.
Farah Alvi 1 2 , Manoj Ram 2 3 , Humberto Gomez 3 2 , Ashok Kumar 2 3
1 Electrical Engineering, University of South Florida, Tampa, Florida, United States, 2 Nanotechnoloy research and Education Center, University of South Florida, Tampa, Florida, United States, 3 Mechanical Engineering, University of South Florida, Tampa, Florida, United States
Show AbstractIn recent years, there has been considerable interest amongst researchers to develop novel inorganic-organic hybrid materials with composition modulated on the nanoscale due to their wide potential applications in display technologies, microelectronics, catalysis, sensors and molecular electronics. The fabrication of nanocomposite films by wet chemical techniques has been proved as a simple and inexpensive strategy than technologically demanding physical methods. Recently, Ram et al have developed metal oxide and conducting polymer nanocomposite films of titanium oxide (TiO2)-PANI, TiO2-polypyrrole, SnO2-polyhexylthiophene, TiO2-poly(thiophene-aniline) nanocomposite, Mn-Ferrite-PANI, MWCNT-Poly(o-anisidine) by wet chemical methods and employed them extensively for gas sensing and molecular electronics applications. It is known that PANI is one of the widely studied materials due to its unique electrochemical, chemical and physical properties. In addition, PANI exhibits high electrical conductivity and good environmental stability in doped and pristine (undoped) states. On the other hand, zinc oxide (ZnO) is a multifunctional semiconducting material with a wide band (3.37 eV at 300 K) and large exciton binding energy (60 MeV). Recently, it has been shown to exhibit several promising prospects for nanoscale structures. Further, using nanocomposite polymer scaffold, it is also possible to increase the properties of PANI as well as ZnO nanomaterials.In this work, initially we have prepared ZnO-PANI nanocomposite films by wet polymerization method. Following this, we have then characterized the ZnO-PANI by UV-Vis, FTIR, cyclic voltammetry, impedance, Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and electrical conductivity. Results confirmed the presence of nano-Schotky junction for the first time in ZnO-PANI samples. The electrochemical investigations revealed that the individual redox properties of ZnO and PANI can be maintained in ZnO-PANI system. Further, results indicated that ZnO-PANI film has exhibited wide potential window. Moreover, we have observed the single layer nano Schottky junction for the first time in the ZnO-PANI film. The photoelectrochemical behavior of ZnO-PANI revealed the faster and two fold current than the polyaniline films. The results confirmed that the ZnO-PANI system has wide potential applications in the design of Schottky diode, photovoltaic and electrochemical capacitors.
9:00 PM - JJ5.39
Surface Nano-structuring of Reverse Osmosis Membranes via Atmospheric Pressure Plasma-induced Graft Polymerization for Reduction of Mineral Scaling Propensity.
Myungman Kim 1
1 Material Research Center, Samsung Advanced Institute of Technology (SAIT), Suwon, Korea Korea (the Republic of)
Show AbstractSurface nano-structuring of polyamide desalination membrane with a hydrophilic poly(methacrylic acid) was shown to reduce the membrane mineral scaling propensity as demonstrated with calcium sulfate dihydrate (gypsum). A two-step approach was employed, whereby the active polyamide (PA) layer of a thin-film composite (TFC) synthesized membrane was activated with impinging atmospheric plasma, followed by a solution free-radical graft polymerization (FRGP) of a water soluble methacrylic acid (MAA) monomer, at 60 °C and initial monomer concentration of 5–20% (v/v), onto the surface of the PA-TFC membrane. The approach of creating a layer of end-grafted poly(methacrylic acid) (PMAA) surface chains was first developed and evaluated using a surrogate polyamide membrane layer interfacially polymerized onto a thin poly(ethyleneimine) (PEI) film coated onto a silicon wafer. The resulting PMAA–PA-PEI–Si surrogate membrane surface was hydrophilic with a water contact angle range of 10–17°. Structuring of the PA-TFC membrane at equivalent FRGP reaction conditions resulted in membranes of higher permeability (by a factor of 1.3–2.26) relative to a commercial RO membrane of a similar surface roughness ( 70 nm) and salt rejection. Flux tests of membrane mineral scaling demonstrated that membrane mineral scaling propensity can be measurably reduced, relative to commercial membrane of the same salt rejection, while yielding equivalent or higher water permeability. The onset time for gypsum scaling for the optimal membrane surface (prepared at 10% (v/v) initial MAA concentration) was retarded by a factor of 2–5 relative to the commercial RO membrane. Current work is ongoing to further optimize the surface structure in order to increasing scaling resistance and assess the impact of surface structuring on nucleation of mineral salt crystals.
9:00 PM - JJ5.4
Nanorods Controlling Phase Morphologies in Two-dimensional Binary Fluid Mixtures.
Egor Maresov 1 , Li-Tang Yan 1 , Anna Balazs 1
1 Chemical Engineering, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
Show AbstractWe developed a theoretical model of immiscible binary polymeric fluid system with immersed nanoscale rods. Two types of rods were considered: the rods A are wetted by the component A of the mixture, while the rods B are wetted by the component B. Surface properties and morphologies of the liquid phases depending on parameters of the rods and their concentration were found. The obtained data were corroborated in the computer simulations. The molten polymer blend was modeled by the cell dynamical system method (CDS), and the nanorods were simulated by the Brownian dynamics (BD) approach. The results of the study might be applied for creating nano-ordered materials, e.g., sustainable composites and photovoltaics.
9:00 PM - JJ5.40
Nanophase Arrangement on Baroplastic Materials.
Sebnem Inceoglu 1 , Taner Aytun 2 , Ari Bilal 1 , Metin Acar 1
1 Polymer Science and Technology Program, Istanbul Technical University, Istanbul Turkey, 2 Materials Science and Engineering Program , Sabanci University, Istanbul Turkey
Show AbstractA novel class of materials called “baroplastic” can be processed by pressure at room temperature instead of high temperature. Baroplastic materials are mainly based on the block copolymers with different topologies containing a high Tg and a low Tg domains in their nanophase-seperated structures. They can exhibit melt-like flow behavior under moderate pressure at ambient temperature through an apparent semi-solid partial mixing mechanism that substantially preserves the mixed Tg. When the pressure is released, the baroplastic retains its molded shape. This opens a new era in plastic materials with the processibility by pressure at room temperature in contrast to traditional thermoplastic processing. In this way, for plastics, the complete multiple recyclability phenomenon can be achieved at room temperature, without degradation. In an attempt to understand the effect of thermal, morphological and rheological behaviors, the pressure induced processability and infinite recyclability of the baroplastic block copolymers were investigated. As atomic force microscope, differential scanning calorimetry and differential thermal analysis characterization results suggest, through pressure induced reorganization of nanophases room temperature processing and infinite recyclability of baroplastics were successfully achieved.
9:00 PM - JJ5.41
Synthesis of One-monomer-thick Two Dimensional Polymers Made of a Host Molecule.
Ilha Hwang 1 , Dami Lee 1 , Youngkook Kim 1 , Kangkyun Baek 1 , Gyeongwon Yun 1 , Kimoon Kim 1
1 National Creative Research Initiative Center for Smart Supramolecules, Department of Chemistry, and Division of Advanced Materials Science (WCU project), Pohang University of Science and Technology, Pohang Korea (the Republic of)
Show AbstractSynthetic two-dimensional (2D) polymers in which planar dimensions are several orders of magnitude greater than thickness are attractive because of their unusual structure and properties. Although numerous approaches have been reported over the last several decades, the synthesis of one-monomer-thick, covalently bonded 2D polymers with a long-range-ordered internal structure has yet to be achieved. Here we present a novel synthetic method of 2D polymers on an atomically flat template-stripped gold (TSG) surface via the cross metathesis of (allyloxy)12cucurbit[6]uril (1) which consists of a rigid disk-shaped host molecule with twelve polymerizable allyl groups at the periphery. To synthesize one-monomer-thick 2D polymers, we first prepared an ammonium-terminated self-assembled monolayer (SAM) on a TSG substrate. Second, an adlayer of 1 formed through hydrogen bonding and charge-dipole interaction between the carbonyl portal of 1 and the terminal ammonium groups on the SAM. Finally, polymerization of 1 was carried out using the Grubbs’ catalyst. The resulting polymers were characterized by various techniques including IR, TEM, and AFM. In addition, the characterization of the 2D polymers after transfer onto other substrates with a PDMS stamp will be presented.
9:00 PM - JJ5.42
Fabrication and Brief Study of Different Morphologies of Polystyrene Nanostructures Using Solution Template Wetting Phenomena in Anodized Aluminum Oxide (AAO).
Siddharth Meshram 1 , Jianyu Liang 1
1 Materials Science and Engineering, Worcester Polytechnic Institute, Worcester, Massachusetts, United States
Show AbstractRecently, organic nanostructures gained a lot of attention in the field of nanoscience and nanotechnology. Among the reported methods, template assisted methods has been investigated as a candidate to fabricate well defined 1-dimensional polymer nanostructures at low cost. However, inconsistent reports on the influence of key fabrication parameters on the morphology and microstructure of the fabricated nanostructures demands systematic study. In this paper, nanoporous alumina templates with uniform nanochannels have been employed as a fabrication platform to study and understand the behavior of polystyrene (PS) solutions of various concentrations within nanochannels. Different morphologies and microstructures of nanostructures have been characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The influence of fabrication parameters will be discussed in detail. Contradictory to some previous reports, our results confirm that stable nanostructures can be formed at low polymer concentrations (less than 10wt %).
9:00 PM - JJ5.43
The Effect of Spin Speed and Solution Concentration on the Directed Assembly of Polymer Blends.
Liang Fang 1 , Ming Wei 1 , Carol Barry 1 , Joey Mead 1
1 Department of Plastics Engineering, NSF Nanoscale Science and Engineering Center for High-Rate Nanomanufactuing, University of Massachusetts Lowell, Lowell, Massachusetts, United States
Show AbstractNanopatterned polymer structures can be produced by directed assembly of polymer blends on chemically functionalized patterns during spin coating. Well-ordered directed morphologies of polymer blends are obtained when the characteristic lengths of polymer blend morphologies are commensurate with pattern periodicities. In this work, spin coating speed and solution concentration were used to control the characteristic length of a polystyrene (PS) / polyacrylic acid (PAA) blend. Critical spin speeds and solution concentrations, which produced the required characteristic length commensurate with the given pattern periodicity, were predicted. Well-ordered morphologies were fabricated when the spin speed and solution concentration were close to the critical values. A new image analysis method was introduced to quantitatively evaluate the directed morphologies. Using this method, the range of commensurability between characteristic length and pattern periodicity for well-ordered morphology was found to be within 20%.
9:00 PM - JJ5.44
A New Subclass of Self-assembling Multidomain Peptides.
Erica Bakota 1 , Jeffrey Hartgerink 1
1 Chemistry, Rice University, Houston, Texas, United States
Show AbstractPeptides are materials that, as a result of their polymeric nature, possess enormous versatility and customizability. Multidomain peptides (MDPs) are a particular class of peptides that form stable, cytocompatible hydrogels. These peptides have an ABA block motif, in which the A block is a series of one or two charged amino acids, such as lysine, and the B block consists of a series of alternating hydrophilic and hydrophobic amino acids, such as glutamine and leucine. In aqueous solution, these peptides self-assemble to form β-sheet fibers, which form an extensive nanofiber network that results in a hydrogel. Previous generations of multidomain peptides incorporated alternating hydrophilic and hydrophobic amino acid residues in the B block of the peptide. Recently, we have substituted aromatic residues for the aliphatic residues, resulting in a new subclass of multidomain peptides (aromatic MDPs) with properties very different from the previous generations. In this work, we have fully characterized this class of aromatic MDPs using circular dichroism, IR spectroscopy, AFM, electron microscopy, and rheometry. The secondary structures of these peptides indicate that the self-assembly process for this subclass differs from the previously published process predicting the formation of β-sheet nanofibers. These aromatic MDPs show a variety of secondary structures via circular dichroism, and these structures can be correlated with fiber formation and morphology, as seen by electron microscopy. The differences between aromatic MDPs and traditional MDPs may prove useful for drug delivery applications or in the field of biocompatible surfactants.
9:00 PM - JJ5.45
Designing Elastin-like, Self-assembling Biomaterials. Sequence and Domain Structure Determine Mechanical Properties of Polymeric Elastomers.
Fred Keeley 1 , Lisa Muiznieks 2 , Ming Miao 3 , Eva Sitarz 4
1 Molecular Structure and Function, Hospital for Sick Children, Toronto, Ontario, Canada, 2 Molecular Structure and Function, Hospital for Sick Children, Toronto, Ontario, Canada, 3 Molecular Structure and Function , Hospital for Sick Children, Toronto, Ontario, Canada, 4 Molecular Structure and Function , Hospital for Sick Children, Toronto, Ontario, Canada
Show AbstractSelf-assembly of monomeric units into organized polymers is currently the subject of much attention, particularly in the areas of nanotechnology and biomaterials. One biological example of a protein polymer with a capacity for self-organization is elastin. Elastin is an insoluble, polymeric, extracellular matrix protein that provides tissues, including large arteries, lungs and skin, with the physiologically important properties of extensibility and elastic recoil. Our research seeks to understand how sequence/structure and domain arrangements in monomeric elastin (tropoelastin) and elastin-like polypeptides (ELPs) both determines their ability to self-assemble into organized matrices and leads to the unusual mechanical properties of such polymeric matrices. Here we describe the mechanical properties of a series of genepin-crosslinked ELPs modeled on sequences and domain arrangements of human tropoelastin, comparing these to the properties of genipin-crosslinked full-length tropoelastin and native polymeric elastin from mammalian, avian and teleost species. In addition, based on information on conserved domains in tropoelastin across a wide range of species, we compare the mechanical properties of ELPs reconstructing a simplified version of tropoelastin.
9:00 PM - JJ5.46
Synthesis and Self-assembly of a Tricyclic G-C Base into Rosette Nanotubes.
Gabor Borzsonyi 1 2 , Andrew Myles 1 , Ross Johnson 1 2 , Jae-Young Cho 1 , Takeshi Yamazaki 1 , Rachel Beingessner 1 , Andriy Kovalenko 1 , Hicham Fenniri 1
1 , National Institute for Nanotechnology, Edmonton, Alberta, Canada, 2 Chemistry, University of Alberta, Edmonton, Alberta, Canada
Show AbstractA tricyclic module functionalized with two allyl groups is described, which features the Watson-Crick H-bond acceptor-donor arrays of both guanine (G) and cytosine (C) positioned on opposite sides of a pyridyl ring. This self-complementary motif, which has been termed ×G-C, is an extended version of the bicyclic G-C molecule that we have previously reported.(1) It was specifically designed to self-assemble into rosette nanotubes (RNTs) having the largest inner diameter reported thus far of 1.4 nm. In this presentation, we describe the self-assembly of ×G-C in DMF and characterize the resulting RNTs using SEM, TEM and AFM techniques. This new construct gives us the opportunity to develop strategies in which to functionalize the RNTs inner channel. Furthermore, because of their larger outer diameter (i.e. reduced functional group density), sterically demanding moieties can be potentially conjugated and displayed on the RNT surface.(1) Fenniri, H.; Mathivanan, P.; Vidale, K. L.; Sherman, D. M.; Hallenga, K.; Wood, K. V.; Stowell, J. G. J. Am. Chem. Soc. 2001, 123, 3854.
9:00 PM - JJ5.47
Strategies for Block Copolymer-inorganic Nanoparticle Coassembly with Tailored Nanoparticle Surface and Polymer Chemistries.
Hiroaki Sai 1 , William Baumgardner 2 , Byung Hyo Kim 3 , Tobias Hanrath 2 , Taeghwan Hyeon 3 , Ulrich Wiesner 1
1 Materials Science and Engineering, Cornell University, Ithaca, New York, United States, 2 Chemical and Biomolecular Engineering, Cornell University, Ithaca, New York, United States, 3 Chemical and Biological Engineering, Seoul National University, Seoul Korea (the Republic of)
Show AbstractBlock copolymers (BCP) provide unique platforms for ordered self-assembled nanostructures on the length scale of 10 to 100 nanometers. By tuning the chemical affinity of the surface of inorganic nanoparticles, ordered inorganic-organic nanocomposite materials can be synthesized which have potential applications in energy conversion, storage, plasmonic metamaterials, and biomaterials. In this work, we present strategic approaches toward a generalized scheme to incorporate pre-synthesized inorganic nanoparticles (metal, metal chalcogenide or metal oxide nanoparticles) into block copolymer mesophases.
9:00 PM - JJ5.48
Relationship between Induced Fluid Structure and Boundary Slip in Nanoscale Polymer Films.
Nikolai Priezjev 1
1 Mechanical Engineering, Michigan State University, East Lansing, Michigan, United States
Show AbstractMicrofluidics is one of the fastest growing technical fields. Its applications include molecular biology, environmental monitoring, microelectronics, and clinical diagnostics. As emphasized in numerous recent reviews on micro- and nanofluidic systems, which are characterized by large surface-to-volume ratios, fluid flow is significantly influenced by boundary conditions. The usual assumption in fluid mechanics textbooks is the no-slip boundary condition, i.e., the tangential speed of the liquid equals that of the adjacent solid surface. Although this assumption is successful in describing fluid flow on macroscopic length scales, it needs revision for microscopic scales due to the possibility of slip of the fluid relative to the wall. Therefore, the central issue for modeling and predicting fluid flows and instabilities in such small-scale systems is how to correct the no-slip assumption. The measure of slippage is the so-called slip length which depends sensitively on several key parameters, such as wettability, surface roughness, complex fluid structure and shear rate.
In this study, we investigate the dynamic behavior of the slip length at the interface between polymer melts and weakly attractive smooth walls using molecular dynamics (MD) simulations. The polymer melt is modeled as a collection of bead-spring linear flexible chains. The MD results show that the slip length passes through a minimum as a function of shear rate and then increases rapidly at higher shear rates. We also found that the slip length depends on the wall lattice orientation with respect to the shear flow direction at sufficiently high shear rates. The range of examined shear rates covers the transition from Newtonian to shear-thinning flow regimes repeatedly observed in experiments.
We demonstrate numerically that the friction coefficient at the polymer-solid interface (the ratio of viscosity and slip length) undergoes a transition from a nearly constant value to the power law decay as a function of the slip velocity. The characteristic slip velocity of the transition is determined by the time needed for fluid monomers to diffuse over the distance between nearest minima of the surface potential. We also show that in the linear regime the friction coefficient is well described by a function of a single variable that depends on the value of surface-induced peak in the structure factor and the contact density of the first fluid layer near the solid wall. The universal relationship between the friction coefficient and induced fluid structure holds for a number of parameters of the interface: fluid density and structure (chain length), wall-fluid interaction energy, wall density, lattice type and orientation, thermal or solid walls.
9:00 PM - JJ5.49
A Nanoscale Interlayer that Raises Response Rate of Holographic Updatable Writing in Photorefractive Polymers.
Hua Zhao 1 , Jingwen Zhang 1 , Xiudong Sun 1 , Baldassare Di Bartolo 2
1 Physics, Harbin Institute of Technology, Harbin, Heilongjiang, China, 2 Physics, Boston College, Chestnut Hill, Massachusetts, United States
Show AbstractReal time holographic updatable display is promising for a variety of applications, such as a spatial 3 dimensional (3D) map that is updatable in near real time (4D). One emerging approach to the development of such a system involves photorefractive polymers that have the properties that can satisfy the challenging requirements imposed on the material platform.[1] In this regard, fast response photorefractive (PR) polymeric composites were reported in the past years, [2,3] ushering practical development of 4D holographic display systems. We report great improvement of the response rate as well as of two beam coupling gain coefficient in the stable polymeric composite with low operation voltage. The specific nanoscale photoconductive interlayer was believed responsible for this dramatic improvement.The selected key experimental results are given in two selected 100 µm thick PR samples made of poly (N-vinylcarbazole (PVK) + pentyl-cyanobiphenyl (5CB) + fullerene (C60). Solution, one with a trinitrofuorene (TNF) + PVK interlayer between ITO layer and PVK + 5CB+ C60 main functional layer, the other without interlayer. The dramatic enhancement of the gain coefficient and increase of response rate caused by addition of the 100 nm thick TNK + PVK interlayer is surprisingly encouraging. It seems that the interlayer provents ion injection from ITO layer into the body of main polymeric layers and the TNF serves as an electron accepter. This might be the reason for the remarkable gain increase as well as the response improvement. For a small crossing angle situation, over 4 to 6 high diffraction orders were observed. This demonstrated the excellent PR properties in the material system from a different perspective. Furthermore, a strong fanning effect had been also observed in the PR samples used. This strong fanning effect had been long regarded as the solid proof for an excellent PR material, since the extensive inorganic PR research era. The time constants of grating formation and erasing in the studied system are functions of applied voltage and can be made as short as few milliseconds at favorable conditions.[1] Savas Tay, P.-A. Blanche, R. Voorakaranam, A. V. Tunc, W. Lin, S. Rokutanda, T. Gu, D. Flores, P. Wang, G. Li, P. St Hilaire, J. Thomas, R. A. Norwood, M. Yamamoto & N. Peyghambarian, “An updatable holographic three-dimensional display”, Nature, 451, 694-698 (2008)[2] Eralp, M., Thomas, J., Tay, S., Li, G., Schülzgen, A., Norwood, R.A., Yamamoto, M. and Peyghambarian, N., “Submillisecond response of a photorefractive polymer under single nanosecond pulse exposure,” Applied Physics Letters, 89, 114105 (2006).[3] Eralp, M., Thomas, J., Tay, S., Li, G., Schülzgen, A., Norwood, R.A., Yamamoto, M. and Peyghambarian, N., “Photorefractive polymer device with video-rate response time operating at low voltages,” Optics Letters, 31, 10, 1408-1410 (2006)
9:00 PM - JJ5.5
Development of a Particle Nano-imprinting Technique by Core-shell Particles.
Hideaki Watanabe 1 , Keiji Fujimoto 1
1 Applied Chemistry, Keio University, Yokohama Japan
Show AbstractIntroduction: A nano-imprinting technique has attracted much attention since it is an easy and low-cost method. We developed a particle nano-imprinting technique, which requires neither masks nor molds for imprinting. Core-shell particles are used instead of masks and molds because the particles can readily adhere to a variety of substrates and it is easy to align them with regular intervals. Therefore, this makes it possible to reduce the number of steps for fabrication of nano-imprinting. In this study, surface nano-structures (e.g., strumas and pores) were fabricated onto flat and uneven surfaces by the particle nano-imprinting technique. It is known that the wettability is significantly improved by the microfabrication of the surface. Thus, we focused on surface wettability as one of applications of nano-fabricated surfaces. Arraying of nanomaterials was carried out into nanopores fabricated by the particle nano-imprinting. We also tried to produce nanocrystals by using nanopores as a reaction vessel with zepto litter volume, which is called “zepto-reactor”. Experiment: Two kinds of core-shell particles (NAG and NG particles) were prepared by soap-free emulsion polymerization. Both particles have a hard core composed of copolymers of glycidyl methacrylate (GMA) and N-isopropyl acrylamide (NIPAM), and a thermo-sensitive shell composed of copolymers of NIPAM and acrylamide (AAm). Particles were closely packed and tightly attached onto a polymer substrate by Langmuir-Blodgett (LB) technique. UV irradiation to particle monolayers was carried out by a high-pressure Hg lamp to obtain patterned indented surfaces. The contact angle measurement for the obtained surfaces was carried out and the surfaces were observed by AFM and SEM.Results and discussion: Nanostrumas and nanopores were formed at the sites where the cores of particles were located by exposing the substrates to UV light. It was found that such nano-patterned surfaces were formed on poly(methyl methacrylate) (PMMA) substrate, poly(ethylene telephthalate) (PET) film, fluorinated films (PFA and FEP) and a curved polystyrene surfaces. The contact angle of the surface with nanostrumas decreased from 70 degree of the particle monolayer to 13 degree, and it increased again to 50 degree by forming nanopores on the surface. We could control adsorption of rhodamine 6G by these nano-structures. The results of AFM also indicated that the nano-patterned surface possessing nanopores of a zepto liter scale was formed by the particle nano-imprinting. It was also found that proteins and magnetic nanoparticles could be arrayed and nanocrystals of NaCl and CaCO3 could be produced by using nanopores (zepto-reactors). We hope that the nanofabricated surface would be applied for advanced materials and devices such as micro flow channels, biochips and novel tissue cultured substrates.
9:00 PM - JJ5.50
Thermoreversible Ion Gels of Triblock Copolymers of Ethylene Oxide and N-tert-butylacrylamide in an Ionic Liquid.
Nitin Sharma 1 , Rubinder Kaur Lakhman 1 , Yuxiang Zhou 2 , Rajeswari Kasi 1 2
1 Polymer Program, Institute of Materials Science, University of Connecticut, Storrs, Connecticut, United States, 2 Chemistry Department, University of Connecticut, Storrs, Connecticut, United States
Show AbstractIonic liquids widely promoted as “green solvents” have attracted much attention for past few decades through their unique physico-chemical properties, excellent chemical & thermal stability, low vapor pressure and high ionic conductivity. They are popular candidates for applications like lithium batteries and gas absorption but face an acute problem in controlling its fluidity resulting into leakage and handling problems. Thus mechanical integrity is one lacking factor in ionic liquids which can be overcome by adding a polymeric material such as block copolymer. One particular reason of adding a block copolymer is to exploit its property of microphase separation to form self-assembled structures in ionic liquid known as “ion-gels”. Ion gels show potential applications in lithium batteries, organic thin film transistors and gas separation membranes. This is a promising and upcoming area of research where there is a need to develop materials which can offer improved properties and mechanical robustness with relatively small quantities of material. In this contribution we report the synthesis of amphiphilic triblock copolymers of ethylene oxide [EO] and N-tert-butylacrylamide [NtBAM] with ethylene oxide as midblock (NtBAMnEOmNtBAMn, m & n are number of repeat units) by reversible addition fragmentation chain transfer (RAFT) technique. Ion gels are formed through the self-assembly of these triblock copolymers in a room temperature ionic liquid, 1-butyl-3-methyl imidazolium tetrafluoroborate ([BMIM][BF4]), which is a good solvent for EO block. Rheological measurements have shown that these ion gels are thermoreversible in nature and gelation temperature (Tgel) is determined by the cross-over of the dynamic moduli (G' & G") at a fixed low frequency on increasing the temperature. We have also demonstrated that we can tune Tgel by varying the solvatophobic acrylamide block length. In summary, we can tailor the processing conditions of these ion gels by tuning the gelation temperature (Tgel) to realize a variety of potential applications.
9:00 PM - JJ5.51
Critical Gel States of Polystyrene-b-poly(N-tert-butylacrylamide) Organogels.
Nitin Sharma 1 , Rajeswari Kasi 1
1 Polymer Program, Institute of Materials Science, University of Connecticut, Storrs, Connecticut, United States
Show AbstractSolution self-assembly of block copolymers has been a subject of research emphasis for last few decades due to their numerous applications such as responsive materials, adhesives, rheology modifiers, drug delivery, gel actuators and microfluidic devices. In this contribution we present here morphology and dynamic viscoelastic studies of polystyrene-b-poly(N-tert-butylacrylamide) (S278NtBAM517 and S93NtBAM252) diblock copolymers in 1-octanol as a function of copolymer concentration. These diblock copolymers in 1-octanol, a selective solvent for N-tert-butylacrylamide block, self assemble to form spherical micelle which is evidenced by transmission electron microscopy (TEM). At higher concentrations, these diblock copolymers in 1-octanol form glass-clear gels. The dynamical arrest of these systems at higher concentrations from their low concentrated micellar solutions is a good example of arrested states of soft matter. Our main thrust in this work is to investigate the formation and properties of critical gel states for SmNtBAMn /1-octanol system. It is well-known that transition of a system from a liquid-like to a solid-like behavior is through a gel point at which it forms a “critical gel”. Critical gels provide characteristics of both, viscous liquid and hookean solid. By knowing the gel point, one can tune the material’s state to include or obviate the chances of gel formation depending on the applications. Here, the gelation variable is concentration and Critical gelation concentration (cg) is determined by frequency independence of loss tangent in the vicinity of gel point and exhibit an increasing trend with temperature, while, material parameters, n and Sc, vary with temperature. In summary, we can tailor the processing conditions of these block copolymer solutions to affect the occurrence of gelation, which can be modified depending on the applications.
9:00 PM - JJ5.6
Supramolecular Block Copolymer Assemblies Aided by Donor-acceptor Interactions.
Alexander Sidorenko 1 , Daniel Hagaman 1 , Timothy Enright 1 , John Tovar 2 , Patricia Peart 2 , Giselle Elbaz 2
1 Chemistry & Biochemistry, University of the Sciences in Philadelphia, Philadelphia, Pennsylvania, United States, 2 Chemistry, Johns Hopkins University, Baltimore, Maryland, United States
Show AbstractThe phenomenon of microphase separation in block copolymers (BCP) is a classic example and illustration of self-assembly in complex systems. If one of the blocks of a block copolymer is selectively modified by hydrogen bonded additive of low molecular mass, a novel class of materials is formed, i.e. supramolecular block copolymer assembly (SMA). Two SMA systems have been investigated in details: poly(styrene-block-4-vinylpyridine) PS-P4VP BCP with pyridine units H-bonded with either n-pentadecyl phenol or 2-(4’-hydroxybenzeneazo)benzoic acid (HABA). The presence of a weakly attached additive in one of the domains significantly modifies the material morphology and properties. A bulky additive increases the volume fraction of the block eventually resulting in the morphology shift. An additive is concentrated within the domains of preferable block of BCP which allows chemical reactions within the domains. Due to the high mobility of H-bonded molecules of the additive, the microphase separation in SMAs occurs quicker and can result in better ordering compared to neat BCPs. The unique properties of the SMAs originate from mobile additives attached by the reversible hydrogen bonds. Here we report on a series of new systems formed in absence of hydrogen bonds. We hypothesize that weak donor-acceptor intermolecular interactions promote formation of these SMAs. The SMAs are composed of PS-P4VP as a polymer part and thiophene-containing additives as a low molecular weight counterpart. More specifically, we tested two commercially available additives: 3,4-(2,2-Dimethylpropylenedioxy)thiophene and hydroxymethyl 3,4-ethylenedioxythiophene. Also, two pi-conjugated substituted oligomeric thiophenes PAP-I and PAP-II were synthesized specifically for the needs of the project. We observed formation of donor-acceptor SMAs using scanning probe macroscopy (SPM), NMR, and spectroscopic ellipsometry. Thin films of all SMAs demonstrate clearly seen microphase separation and self-assembly similar to neat BCPs. The SMAs formed between the BCP and additives revealed significant increase in periodicity of the nanodomains. Further work on donor-acceptor SMAs is in the progress.
9:00 PM - JJ5.7
Polymer-nanotube Thin Film Assemblies with High Transparency and Low Sheet Resistance for ITO Replacement.
Jaime Grunlan 1 2 3
1 Mechanical Engineering, Texas A&M University, College Station, Texas, United States, 2 Chemical Engineering, Texas A&M University, College Station, Texas, United States, 3 Materials Science and Engineering Program, Texas A&M University, College Station, Texas, United States
Show AbstractTransparent electrodes made from metal oxides suffer from poor flexibility and durability. Highly transparent and electrically conductive thin films were assembled as a potential indium tin oxide (ITO) replacement using layer-by-layer (LbL) assembly of single-walled carbon nanotubes (SWNTs), stabilized with negatively-charged deoxycholate (DOC), and positively-charged poly(diallyldimethylammonium chloride) [PDDA]. Ellipsometry, quartz crystal microbalance, and UV-vis were used to measure the linear growth of these films as a function of the number of bilayers deposited, while TEM and SEM were used to visualize the morphology of these films. The PDDA/(SWNT+DOC) system produced transparent (> 82% visible light transmittance) and electrically conductive (~ 160 S/cm) 20-bilayer films with a 38.4 nm thickness. Moreover, a series of post treatments, involving heating and nitric acid doping, were used to increase conductivity to 1430 S/cm (Rs ~ 300 Ω/sq), with no change in transparency, owing to the removal of PDDA and the charge transfer doping. This study demonstrates high visible light transmittance and electrical conductivity of SWNT-based thin films, which are potentially useful as flexible transparent electrodes for a variety of optoelectronic applications.
9:00 PM - JJ5.8
Multiscale Directed Assembly of Polymer Blends on Nanoscale Patterned Self-assembled Monolayers.
Jason Chiota 1 , John Shearer 1 , Ming Wei 1 , Carol Barry 1 , Joey Mead 1
1 Plastics Engineering, University of Massachusetts Lowell, Lowell, Massachusetts, United States
Show AbstractNanopatterned polymer structures can be used in a variety of applications from nanolithography to biomedical. This study focused on the rapid directed nanoscale assembly of polystyrene (PS)/polymethyl methacrylate (PMMA) blends into complex patterns of nonuniform geometries at multiple length scales on a single template. The patterns were created using alkanethiols on gold templates patterned by Dip-Pen Nanolithography (DPN). These chemically functionalized nanotemplates directed the nanoscale assembly of polymer blends into nonuniform patterns in short times (less than one hour). Attraction between the polymer and patterned surface controlled the deposition of hydrophilic polymers onto the hydrophilic regions of the template, while hydrophobic polymers were assembled onto the hydrophobic regions. Length scales from 300 nm down to 100 nm and nonuniform geometries were consistently patterned on the same template. Domains sizes down to 50 nm were also replicated into complex nonuniform geometries, but less consistently compared to the larger sizes. This assembly achieved smaller sizes and more complex geometries than have previously been reported utilizing polymer blends. These results provide a process is capable of assembling polymer blends into varying geometric structures in a relatively simple, rapid, and consistent fashion suitable for scale-up in a nanomanufacturing process.
9:00 PM - JJ5.9
Hierarchical Nanostructures by Double Templated Self-assembly of Si-containing Block Copolymers.
Jeong Gon Son 1 , Adam Hannon 1 , Kevin Gotrik 1 , Caroline Ross 1
1 Department of Materials Science & Engineering, MIT, Cambridge, Massachusetts, United States
Show AbstractSelf-assembly of block copolymers can be used to generate periodic patterns with feature sizes of a few nm and above, and has great promise in nanoscale lithography. Block copolymers with one Si-containing block are particularly attractive due to their high etch contrast and high interaction parameter, which leads to a sharp interface between the microdomains. Templating of these materials has been carried out using topographical or chemical patterns, typically written by electron-beam lithography. However, as the periodicity of the microdomains decreases, templating becomes more challenging. In this work, we present a strategy for templating of small period (12-17 nm) block copolymers using a topographical pattern formed from a larger period (34-40 nm) block copolymer. The larger period block copolymer can itself be templated using features produced by electron-beam lithography or photolithography, resulting in a hierarchical method for pattern generation. This process is demonstrated using poly(styrene-block-dimethylsiloxane) (PS-b-PDMS). A 45.5kg/mol PS-PDMS was self-assembled to form a monolayer of in-plane cylinders of PDMS in a PS matrix, aligned with topographical templates made using photolithography. Annealing in a toluene vapor then oxygen etching of the film left oxidized PDMS topographical grating patterns of period 34–40 nm. Alternatively, a perforated lamellar pattern could be produced by annealing in a mixture of toluene and heptane vapor. The 45.5kg/mol pattern was coated with a PDMS brush, then a 16kg/mol PS-PDMS was spin-coated and annealed. The 16kg/mol PS-PDMS has a period approximately half that of the 45.5kg/mol PS-PDMS, and its self-assembled microdomains aligned with the topographical pattern to produce very well-ordered arrays of either cylinders or spheres with period 17 nm. The morphology depended on the solvent anneal conditions: annealing in acetone gave cylinders, whereas annealing in DMF gave spheres.To further explore the hierarchical double-templating process, the effect of commensurability between the two block copolymers was studied by varying the period of the 45.5kg/mol patterns. Defect levels in the templated 16kg/mol pattern were very low when the period of the 45.5kg/mol pattern was within 10% of twice the period of the 16 kg/mol pattern. Additionally, the lowest defect levels in the 16 kg/mol pattern occurred at a duty cycle of the 45.5kg/mol pattern around 50%. 12kg/mol and 8kg/mol PS-PDMS were also templated on the 45.5kg/mol patterns. The period of these smaller block copolymers is incommensurate with that of the template, and patterns formed such as two rows of spheres on the mesas and one row in the trenches. This process generated a range of hierarchical nanostructures, including small period grating line structures, dots-on-lines or dots-in-holes. Simulation of this double templated self-assembly based on Self Consistent Field Theory (SCFT) agreed with the experimentally determined morphologies.
Symposium Organizers
Padma Gopalan University of Wisconsin-Madison
Qing Wang The Pennsylvania State University
Hilmar Koerner U. S. Air Force Research Lab/RXBN
Dhandapani Venkatraman University of Massachusetts Amherst
Teruaki Hayakawa Tokyo Institute of Technology
JJ6: Nanoporous Materials I
Session Chairs
Thursday AM, December 02, 2010
Independence W (Sheraton)
9:15 AM - JJ6.1
Highly-ordered Porous Coordination Polymer Nanofilms Grown by Layer-by-layer Deposition Technique.
Rie Makiura 1 2 , Hiroshi Kitagawa 2 3
1 Nanoscience and Nanotechnology Research Center, Osaka Prefecture University, Sakai, Osaka, Japan, 2 , JST-CREST, Tokyo, Tokyo, Japan, 3 Division of Chemistry, Kyoto University, Kyoto, Kyoto, Japan
Show Abstract The rational assembly of ultrathin films of porous coordination polymers (PCPs) – highly ordered microporous materials – with well-controlled growth direction and film thickness is a critical issue for the use and integration of PCPs in future nanotechnological devices, such as sensors, catalysts, and electrodes for fuel cells. Here we report the facile bottom-up fabrication at ambient temperature of such a perfect preferentially-oriented PCP nanofilm on a solid surface (NAFS-1), consisting of metalloporphyrin building units (ref.1). The construction of crystalline NAFS-1 was achieved by the unique combination of a Layer-by-Layer (LbL) growth technique coupled with the Langmuir-Blodgett (LB) method (LB-LbL). NAFS-1 assembles in a complete directionally-controlled manner and is endowed with highly crystalline order both in the out-of-plane and in-plane orientations to the substrate, as determined by synchrotron X-ray surface crystallography.Reference1) R. Makiura et al. Nature Mater., in press doi: 10.1038/nmat2769 (2010)
9:30 AM - **JJ6.2
A Novel Route to the Preparation of Nanoporous Bi-continuous Polymer Membranes.
Easan Sivaniah 1
1 Department of Physics, Cavendish Laboratory, University of Cambridge, Cambridge United Kingdom
Show AbstractWe report of the production of nanoporous polymer membranes that have a bi-continuous morphology. The resulting membranes are then transformed into a number of different scaffold materials, including metal oxides and metals. The use of the transformed materials and the initial polymer templates are demonstrated in solar cell and filtration applications.
10:00 AM - **JJ6.3
Multiblock Polymers for Nanoporous Membranes, Monoliths, and Masks.
Marc Hillmyer 1
1 Department of Chemistry, University of Minnesota, Minneapolis, Minnesota, United States
Show AbstractBlock polymers that contain a sacrificial component are finding wide utility in technologies ranging from liquid purification to nano-patterning. Diblock copolymers that contain a robust matrix segment end-coupled to an etchable segment are the most commonly employed systems and can lead to nanoporous materials with, for example, cylindrical pores hexagonally packed in a continuous matrix. Block polymers that incorporate three or more chemically distinct segments hold tremendous promise for the generation of more exotic and even more promising porous structures. As an example, using ABC triblock terpolymers, nanoporous A matrix materials with specific pore wall functionality B can be generated by selective removal of C. Furthermore, by incorporating other functional attributes into these segments (e.g., etch contrast or ability to crosslink), the applicability of such systems can be tremendously enhanced. Motivated by the tremendous technological potential of nanoporous materials from block polymer precursors, we have continued to explore the incorporation of multiple functional blocks into these hybrid macromolecules that (i) expand the range of accessible nanostructures and (ii) contain the chemical functionality essential for a particular targeted application. These efforts necessitate the controlled synthesis of multiblock polymeric materials from a broad pallet of monomers. In this talk I will discuss our recent efforts in the precision synthesis and detailed characterization of such nanostructured polymeric materials and highlight their usefulness in applications that include magnetic material patterning, water ultrafiltration, and confined crystal growth.
10:30 AM - JJ6.4
Self-assembly of Binary Mixtures of PCL-PEO Copolymers.
Peter Schuetz 1 , Michael Butler 1 , Martin Greenall 2 , Martin Buzza 3 , Thomas McLeish 4
1 Discover, Unilever R&D Colworth, Sharnbrook, Bedfordshire, United Kingdom, 2 Theory of Soft Matter and Biophysics, Forschungszentrum Julich, Julich Germany, 3 Department of Physics, The University of Hull, Hull United Kingdom, 4 Department of Physics, Durham University, Durham United Kingdom
Show AbstractThe mechanisms and rules governing the spontaneous formation of structure from polymeric building blocks with amphiphilic character are challenging and fast moving area. We showed previously that the pathway of self-assembly is a crucial parameter to understand the encapsulation results in the corresponding bulk systems (Adams, D. J.; Adams, S.; Atkins, D.; Butler, M. F.; Furzeland, S. Impact of mechanism of formation on encapsulation in block copolymer vesicles. Journal of Controlled Release 2008, 128 (2), 165-170).Building on this, we now explore binary mixed systems of poly(ethylene oxide)-b-poly(caprolactone) block co-polymers in dilute solution. We describe in both experiment (kinetically controlled self-assembly of polymers mixed at different solvent conditions) and theory (real-space density functional theory), how the controlled blending of co-polymers allows the introduction of new parameters (additional to co-polymer architecture) to determine the shape of the resulting aggregates. We show that the while some mixtures behave similar to one component systems with the corresponding averaged block-length, others show new shapes with non-uniform surface curvature such as “bulbed” rod and rings (similar to the ones described for re-hydrated poly(ethylene oxide)-b-poly(butadiene) systems described by Jain et al. (Jain, S.; Bates, F. S. Consequences of nonergodicity in aqueous binary PEO-PB micellar dispersions. Macromolecules 2004, 37 (4), 1511-1523).
10:45 AM - JJ6.5
Nanostructured Block Copolymer Materials as Ultrafiltration Membranes.
Rachel Dorin 1 , Joerg Werner 1 , William Phillip 3 , Menachem Elimelech 3 , Eric Hoek 2 , Ulrich Wiesner 1
1 Materials Science and Engineering, Cornell University, Ithaca, New York, United States, 3 Civil and Environmental Engineering, UCLA, Los Angeles, California, United States, 2 Chemical and Environmental Engineering, Yale University, New Haven, Connecticut, United States
Show AbstractWater purification is a pressing global issue for the 21st century as the world’s population continues to increase and clean water resources become scarce. Ultrafiltration membranes from polymeric materials with pore sizes <20 nm offer a route to removing many disease-causing parasites from water, but understanding the relationship between macromolecular structure and function has remained a challenge. Here we describe the fabrication of a model ultrafiltration system using a diblock copolymer and small molecule additives. The resulting membranes have highly uniform pore sizes and fabrication is facile and scalable. The membranes have tunable structural properties including pore size, surface chemistry, and mechanical stability, offering a pathway to correlate molecular structure and performance.
11:30 AM - JJ6.6
Mesoscale Simulation of the Self-assembly of Peptide-conjugated Poly(L-lactide) Macromers.
Seyed Sina Moeinzadeh 1 , Esmaiel Jabbari 1
1 Chemical Engineering, University of South Carolina, Columbia, South Carolina, United States
Show AbstractBiodegradable Nanoparticles are being used extensively in drug delivery systems due to their unique properties including size, drug encapsulation, degradability and selectivity. In this work we have simulated the self-assembly of peptide-conjugated acrylated poly(L-lactide) (PLAA) macromers to from nanoparticles (NPs) in aqueous solution, via the Dissipative Particle Dynamics(DPD) method which allows focusing on the larger time/length scales. The system components were coarse-grained into different beads (set of atoms) which moved according to the Newton’s equations of motion integrated via a modified Velocity-Verlet algorithm. The force acting on each bead, in a specific cutoff distance (rc), was divided into conservative force (FC), random force (FR), dissipative force (FD) , bond force (FS) and bond angle force (FE). The parameters of the FR and FD were chosen such that they acted as a statistical thermostat. The repulsion parameters of the FC (αij) were calculated from the solubility parameters of different beads, each of which were extracted from an atomistic molecular dynamics simulation (MD) considering the COMPASS forcefield and QEq charge algorithm. The DPD simulations were done at 298K, in a box with the periodic boundary condition in all three directions. The density of the beads was chosen to be 3/ rc3. The effect of different parameters including compositions, polymer molecular weights as well as the simulation time on the self-assembly and the morphology of aggregates have been investigated and the results agreed well with the experimental results. The formation of NPs or other vesicular structures strongly depended on the system composition. The hydrophilic peptide beads positioned on the surface of the NPs and facing the aqueous solution, acted as a stabilizer and caused the size of the conjugated NPs to be significantly less than the PLAA NPs with narrower distribution. The hydrophobic polymer beads on the other hand formed an internal compacted layer.
11:45 AM - **JJ6.7
New Opportunities in Degradable Block Copolymers: Poly(vinyl esters).
Mahesh Mahanthappa 1 , Corinne Lipscomb 1 , Milton Repollet-Pedrosa 1
1 Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin, United States
Show AbstractPoly(vinyl esters) are widely used commodity polymers in applications ranging from adhesives and paper coatings to chewing gum bases and formulation agents for drug delivery. In spite of the facility with which they degrade under both mild chemical and biological conditions to generate a carboxylic acid and biodegradable poly(vinyl alcohol), synthetic access to well-defined poly(vinyl ester) homopolymers and block copolymers has been limited. This talk will highlight new advances in the syntheses of these materials and related block copolymer surfactants, their ability to self-assemble as polymer melts, and their unusual bulk properties and dilute solution behaviors.
12:15 PM - JJ6.8
Polymer-clay Nano Brick Wall Thin Films as Flexible and Transparent Gas Barrier.
Jaime Grunlan 1 2 3
1 Mechanical Engineering, Texas A&M University, College Station, Texas, United States, 2 Chemical Engineering, Texas A&M University, College Station, Texas, United States, 3 Materials Science and Engineering Program, Texas A&M University, College Station, Texas, United States
Show AbstractThin composite films of branched polyethylenimine (PEI), polyacrylic acid (PAA) and sodium montmorillonite clay (MMT) platelets were prepared using layer-by-layer assembly. Film thickness, mass deposited per layer, and barrier were shown to increase exponentially with the number of deposition cycles. After 32 layers (i.e., eight PEI/PAA/PEI/MMT quadlayers [QL]) are deposited, the resulting transparent film exhibits an oxygen transmission rate (OTR) of 0.03 cm3/m2/day, as shown in the figure below. This 8QL film is ~ 200 nm thick, which makes its permeability lower than that of SiOx reported in the literature. Unlike inorganic oxides, this film is highly flexible and deposited under ambient conditions. This level of oxygen barrier is believed to be due to a nano-brick wall microstructure comprised of exfoliated clay bricks in polymeric mortar, where the enhanced spacing between MMT layers, provided by PEI and PAA, creates channels perpendicular concentration gradient that delay the permeating molecule. Similar films with super oxygen barrier have been prepared using only PEI and clay. These nano-brick wall thin film assemblies are good candidates for flexible electronics, food, and pharmaceutical packaging due to their transparency, super gas barrier (that rivals SiOx) and lack of metal (for microwaveability).
12:30 PM - JJ6.9
Study of Selectively Permeable Coatings to Textiles.
Joseph Sargent 1 , Michael Gilbert 2 , Emmanuelle Reynaud 1 , Jun Lee 3
1 Mechanical engineering, UMass Lowell, Lowell, Massachusetts, United States, 2 , EIC Laboratories Inc., Norwood, Massachusetts, United States, 3 Plastics Engineering, UMass Lowell, Lowell, Massachusetts, United States
Show AbstractBreathable barrier textiles for both chemical agent and moisture are actively developed for military and industry applications. An ideal approach is to coat textiles with a semi-permeable film that allows the transport of water while still serving as a barrier for chemical agents. Sulfonated poly (styrene-isobutylene-styrene) copolymer (SIBS) is spontaneously phase-separating upon drying from solution to produce a nanostructured film that is selectively permeable to water but repels chemical agents. The objective of this research is to investigate coating uniformity and phase morphology of SIBS coating materials fabricated by novel solvent combinations. Scanning electron microscopy (SEM) analysis enables to assess the coating uniformity as well as the level of adhesion between the polymer coating and the fabric substrate. Transmission electron microscopy (TEM) is used to characterize the phase separation morphology of the SIBS copolymer coating. The mechanical behavior of the coated fabric is determined through tensile, shear and friction tests, and compared to the bare fabric behavior. The sum of these results will be used to identify optimized solutions relevant to the need for protective fabrics in military applications.
12:45 PM - JJ6.10
Nanoporous Polyethylene Glycol Filtration Membranes Fabricated by Double Templating.
Krissada Surawathanawises 1 , William Van Geertruyden 1 , Xuanhong Cheng 1
1 , Lehigh University, Bethlehem, Pennsylvania, United States
Show AbstractNanoporous membranes with uniform pore sizes and high porosity are one of the key components in many biomedical applications such as filtration and bioseparation. Although nanofiltration is widely used in the biopharmaceutical industry, there is still a big room for improvement in the physical and chemical properties of existing nanomembranes. In this work, we describe the fabrication of a new nanoporous membrane made in polyethylene glycol (PEG) with uniform pore size, straight cylindrical pore structure, high porosity, flexible mechanical property and desirable biocompatibility, suitable for bioseparation and biosensing applications. Our process involves double replication starting from an anodic aluminum oxide (AAO) membrane master template. Through three-step anodization of aluminum in selective acids and under controlled voltages, we first fabricated AAO membranes with self-order pore arrays, cylindrical pore geometry, extremely high porosity, tunable pore size and controllable thickness supported on aluminum. This is followed by UV-polymerizing methyl methacrylate (MMA) monomer infiltrated into the pores. After etching the aluminum and aluminum oxide layers in acids, an array of poly(methyl methacrylate ) (PMMA) nanopillars were obtained. Next, the PMMA nanopillar array were treated by corona discharge to improve its hydrophilicity and a PEG solution containing a photo initiator and crosslinker was spin coated on top of it. After UV-exposure to crosslink PEG, PMMA nanopillars were dissolved in acetone, releasing stand-alone thin PEG membranes.We characterized the nanostructured materials in each step described above by scanning electron microscopy (SEM). Anodized at 195V in phosphoric acid, the resulting AAO membranes contain densely packed polycrystalline pore arrays with uniform pore sizes of 150 nm in diameter. These pores can be further widened to 200 nm in phosphoric acid. In addition, it was found that AAO grew to around 1 um thick with straight pores in 30 minutes. Using such AAO membranes as the template, dense PMMA nanopillar arrays of aspect ratio around 5 have been obtained reliably in a large surface area. However, PMMA nanopillar arrays with aspect ratio above 10 often collapse, which may put an upper limit to the thickness of the double templated membranes. After the second replication step using the PMMA pillar arrays as the templates, we obtained PEG membranes of similar morphology to the starting AAO material. In some cases, the PEG membranes have pores wider than those of the AAO templates, likely due to the polymer shrinkage after solvent evaporation. Evaluation of the PEG membrane performance is underway in terms of their filtration rate, bioseparation efficiency and fouling property. The preliminary results suggest that PEG membrane is promising for biological filtration and separation applications.
JJ7: Nanoporous Materials II
Session Chairs
Thursday PM, December 02, 2010
Independence W (Sheraton)
2:30 PM - JJ7.1
Self-organized Structures on PDMS for Large Area Optical Applications.
Patrick Goerrn 1 , Marcus Lehnhardt 2 , Wolfgang Kowalsky 2 , Thomas Riedl 3 , Sigurd Wagner 1
1 Department of Electrical Engineering , Princeton University, Princeton, New Jersey, United States, 2 Institut für Hochfrequenztechnik, TU Braunschweig, Braunschweig Germany, 3 Institute of Electronic Devices, University of Wuppertal, Wuppertal Germany
Show AbstractWe studied the formation of surface layers hardened by plasma-enhanced oxidation of the silicone elastomer poly(dimethylsiloxane), experimenting over the broadest range of surface-modifying parameters reported to date. The surface layers may wrinkle, crack, or both, under conditions that at times are controlled by design, but more often, have been discovered by trial-and-error. We find four distinct topographies: flat / wrinkled / cracked / cracked and wrinkled. Plasma dose and pressure were identified as the key variables in the skin forming process. We analyzed wrinkle amplitude and wavelength by Atomic Force Microscopy in the tapping mode. From these dimensions we calculated the elastic modulus and thickness of the hard surface layer. The resulting findings enable a better understanding of wrinkle and crack formation on elastomeric surfaces as well as the identification of the parameters under which the technologically important pure wrinkled, crack-free topography is obtained.This topography enables sinusoidal surface modifications with periods as low as 250 nm. The self-organized gratings could be applied as optical diffraction gratings or resonators. However for this purpose the dislocation density of the self-organized gratings needs to be minimized. We optimized gratings of a period of 420 nm to obtain a dislocation density as low as 1.2x10^4 mm^-2. By depositing an organic gain medium on top of such gratings we build organic distributed feedback lasers. The laser exhibits a low lasing threshold of 28 μJ/cm^2. As the period of a distributed feedback laser sets its wavelength the elastic lasers can be optically tuned by mechanical strain. Uni-axially stretching the laser by 2.2 % tunes its emission wavelength from 633.6 nm to 638.3 nm (4.7 nm). These results demonstrate the outstanding level of ordering that can be achieved by self-organization.To prepare the gratings the surface of a stretched poly(dimethylsiloxane) membrane was hardened by plasma oxidation, and then released. The simple fabrication of the lasers on potentially large areas enables entirely new applications like strain sensing optical skin for structural health monitoring.
2:45 PM - JJ7.2
Nano Patterning on Surfaces of 3-D Micro Structures by Means of Block Copolymer Self Assembly.
Shinichi Warisawa 1 , Hiroyuki Mino 1 , Reo Kometani 1 , Sunao Ishihara 1
1 Department of Mechanical Engineering, The University of Tokyo, Tokyo Japan
Show AbstractRecent block copolymer self-assembly researches have demonstrated the potential to form aligned line patterns, periodical sphere structures, and directed line and sphere patterns using chemical and physical templates at nano scale. All of these, however, have only been examined on two-dimensional flat substrates. Enhancing the potential of nano patterning onto 3-D structures may extend further applications such as wiring for electro circuits on nano- and micro-electro mechanical systems, and 3-D structured high-density memory devices. In this research, we offers the possibility of nano-scale patterning on the surfaces of the 3-D micro structures by block copolymers. The block copolymer used in our experiments is PS-b-PMMA (PS:PMMA = 50k:21k) to form vertical cylinders of PMMA in a matrix of PS. The 3-D micro structures with different angled slopes such as 70, 80, and 90 degrees are prepared on Si substrates by means of a focused-ion-beam chemical-vapor-deposition (FIB-CVD) technique. The material of the 3-D micro structures is diamond-like carbon (DLC) due to selecting phenanthrene as a gas source. Since our preliminary experiments showed that the spin-coating process generally used on a flat substrate was found not applicable to the surfaces of 3-D micro structures, we employ a dip-coating process instead in order to coat copolymers along the surfaces of the 3-D micro structures. In concrete, PS-r-PMMA is dip-coated along the DLC surfaces, and then PS-b-PMMA is dip-coated followed by appropriate annealing. The procedures based on dip-coating can also form nano-patterns on the surfaces of the 3-D micro structures, but they are sparser than expected. It is likely because the surface energy of DLC is low, and thus the coated film thickness is uneven. Then, for the remedy, we employ Au instead of PS-r-PMMA: Au is deposited 100nm in thickness on the DLC surfaces by sputtering, and then PS-b-PMMA dip-coat is employed. After appropriate annealing and PMMA removal processes, we observe the surfaces by FE-SEM. As a result, self-assembled patterns are found to form regularly and densely on every slope surface. Furthermore, the self-assembled patterns are formed in a same way regardless of the places, i.e., top, middle, and bottom on the slope. In summary, we succeed in forming nano pattern on the surface of the 3-D micro structure using dip-coat process with Au deposition instead of random copolymers. The ability to form nano patterns on the surfaces of the 3-D structure using self-assembly materials opens new possibilities of nano fabrication.
3:00 PM - **JJ7.3
Directed Assembly of Block Copolymers and Molecular Transfer Printing.
Paul Nealey 1
1 Chemical and Biological Engineering, University of Wisconsin, Madison, Wisconsin, United States
Show AbstractDirected assembly presents opportunities to enhance or augment the capabilities of the lithographic process. Compelling motivation for directing the assembly of block copolymers, or block copolymer mixed with solvents, homopolymers, or other diluents, is that the intrinsic properties of these self-assembling systems lend themselves to strategies for precise control over the shape, size, and dimensional uniformity of patterned features, and to improved overall resolution of the lithographic process itself. Already the directed assembly of block copolymer films on lithographically-defined chemically nanopatterned surfaces meets essential attributes of manufacturing and is being developed for applications in bit patterned media and integrated circuits (Directed assembly is included as a potential lithography solution in the 2007 and 2009 ITRS Roadmap.) Recently we have extended our approach in directing the assembly of block copolymer films beyond the fabrication of sacrificial templates or soft etch masks. Specifically we are addressing challenges in creating and replicating patterns of diverse chemical functional for a broad spectrum of nanoscale applications from biology to flexible electronics to plasmonics. Our research revolves around a new soft lithographic platform called molecular transfer printing (MTP). Master patterns in the domain structure at the surface of assembled films of block copolymers are transferred with high fidelity to substrates brought into contact with the master film using reactive inks segregated into nanoscale block copolymer domains. The technique is massively parallel and has been demonstrated for dense periodic and geometrically complex patterns with feature dimensions below 15 nm. Here we discuss the transfer of just one ink and the ability to fill the interspatial regions of the pattern with a second ink, and how this strategy has been applied towards creating patterns with diverse chemical functionality on varied substrate materials.
3:30 PM - JJ7.4
Fabrication of Periodic Arrays of 30 nm Inverted Pyramids using Block Copolymer Self-Assembly
Kevin Gotrik 1 , Jeong Gon Son 1 , Brent Keller 1 , Caroline Ross 1
1 MS&E, MIT, Cambridge, Massachusetts, United States
Show AbstractThe self-assembly of block copolymer (BCP) films is becoming an increasingly important technique for nanofabrication due to its ability to create regular arrays of 10 - 100 nm scale features. We report the fabrication of regular arrays of inverted pyramids of period 40 nm etched into Si using the self-assembly of perforated lamella phase poly(styrene-b-dimethylsiloxane) (PS-PDMS) diblock copolymer, which exhibits a large Flory-Huggins interaction parameter (~0.26). These topographical substrates are then used to template the dewetting (agglomeration) of metal films to form metal nanoparticle arrays. The ability to create regular arrays of metal nanoparticles is important due to the broad range of applications in the fabrication of plasmonic waveguides, magnetic memory arrays, and as growth catalysts for semiconductor nanowires and carbon nanotubes.The (100) Si substrates had a 10 nm thick film of PECVD-grown silicon nitride. A 50 W O2 plasma is applied for 5 s to prepare the surface for the hydroxyl-terminated PDMS homopolymer which is spin cast and annealed for 15 hr to form a 2 - 4 nm thick brush layer on the nitride film. PS-PDMS films (45.5 kg/mol, f_PDMS = 0.3) were spuncoat onto the substrate and self-assembled under a mixed solvent vapor of toluene and heptane (~2:1 ratio) that is controlled using a mass flow control system with feedback from spectral reflectance to measure the in situ film thickness. The PS-PDMS forms a bulk cylindrical morphology, but under this solvent anneal process, a metastable perforated lamellar phase forms consisting of an in-plane lamella of PDMS with close-packed perforations of 40 nm period. CF4 and O2 reactive ion etching (RIE) removes the PS block leaving a film of oxidized PDMS with evenly spaced holes. An anisotropic RIE using CF4 at a higher voltage (100V) transfers the evenly spaced hole pattern to the underlying silicon nitride film. Buffered HF acid (2%) removes the remaining oxidized PDMS and prepares the exposed bare silicon surface by removing any native oxide. 1 M KOH is used to anisotropically etch the Si for 3 min leaving behind inverted pyramids 28 nm deep. 50% HF acid is then used to etch away the remaining silicon nitride leaving an array of pyramids suitable for dewetting experiments. The process is compared to an alternative route in which a dot pattern of PDMS from a spherical-morphology 51kg/mol PS-PDMS BCP is transferred into a Ni film to form an etch mask. The 40 nm period inverted pyramids are subsequently coated with metal films which are annealed to induce dewetting, forming arrays of metallic nanoparticles, one in each inverted pyramid. The dewetting process is compared to that which occurs on 100 – 200 nm period inverted pyramids formed by interference lithography. This work demonstrates the utility of BCP-assisted pattern transfer to yield large area nanostructures with dimensions <30 nm.
3:45 PM - JJ7.5
High Density Array of Silver Nano Cluster by Using Crew-cut Type Block Copolymer Micelle for SERS Substrate.
Won Joon Cho 1 , Jin Kon Kim 1
1 Chemical Engineering, POSTECH, Pohang Korea (the Republic of)
Show Abstract Surface enhance Raman scattering (SERS) substrates have been fabricated by either bottom-up method or top-down approach. The former, for instance particle growth in a solution, is very easy, but the uniformity of the size and the inter-particle distance becomes very poor. Thus, only a few places play as a role of the hot spots. On the other hand, the latter based on electron-beam lithography allows one to have precise control of nano-pattern. But, the fabrication of nano particles (or patterns) with an inter-particle (or pattern) distance down to 10 nm on a large area (several cm2) is very difficult. In this study, we solve both problems by fabricating the high density array of silver nano clusters by using crew-cut type polystyrene-block-poly(4-vinylpyridine) copolymer (PS-b-P4VP) micelles. Silver ions (Ag+) were coordinated with poly(4-vinylpyridine) chains, and reduced to silver nanoparticles after reduction with sodium borohydride. The inter-particle distance was carefully adjusted by using different block ratios and total moleculear weights of PS-b-P4VP. After micelle solutions were spin-coated on Si wafer to form the monolayer of the micelles, the block copolymer was removed completely by reactive ion etching (RIE). Silver cluster was analyzed by high resolution Transmission Electron Microscopy and (SERS) effect was measured through all sample areas. We obtained a maximum SERS enhancement factor up to ~108 with an excellent reproducibility.
4:30 PM - **JJ7.6
Striving for Sub-30 nm Resolution: Directed Assembly Meets Self Assembly.
Christopher Ober 1 , Michelle Chavis 1 , Evan Schwartz 1 , Marvin Paik 1
1 Materials Science & Engineering, Cornell University, Ithaca, New York, United States
Show AbstractBlock copolymers make excellent self-assembling materials for nanopatterning. To date, most studied systems are weakly phase separated, non-polar photoinert polymers. Here we discuss block copolymers consisting of a polar, functional block and a non-polar degradable block. An example of such polymers includes poly(α-methyl styrene-block-hydroxy styrene). This polymer can undergo photochemical reactions through the hydroxy function of the hydroxy styrene block. Long range order can be induced through the use of appropriate solvent annealing conditions. We will discuss the lithographic behavior of these materials using high resolution, negative tone photochemistry. These materials, because of the need to dimensional stability and the higher Tg values of many polar systems cannot undergo thermal annealing without degradation of the photoactive components. As a result we have turned to solvent annealing which enables the formation of films with long range order under very benign conditions. We have demonstrated the morphology switching of these materials the use of sequential solvent annealing steps. The study of the solvent annealing of these polymers using grazing incidence (GI) SAXS and other polar-non-polar combinations will also be discussed.
5:00 PM - JJ7.7
Hydrogel Stamping for Patterning of Polyelectrolyte Multilayers.
Chungyeon Cho 2 , Nicole Zacharia 1 2
2 Materials Science and Engineering Program, Texas A&M, College Station, Texas, United States, 1 Mechanical Engineering, Texas A&M, College Station, Texas, United States
Show AbstractPolyelectrolyte multilayers (PEMs) are films that result in a direction of the complexation of oppositely charged polymers; a bottom-up assembly process. Soft lithography is a top-down method for creating structure in thin films. Our work is a combination of the two in order to create novel film structures and functionalities. Patterning of soft films, especially their bulk and not only their surface properties, presents a challenge. Several lithographic techniques do exist, but many of them are complex or limited in their ability to change properties. A few methods of patterning PEMs have been reported, including microcontact printing and selectively growing layers on patterned self-assembled monolayers, but these all come with certain limitations. We present here a modified microcontact printing method, reactive wet stamping (r-WETs), using a hydrogel stamp soaked in aqueous solutions to create patterns in PEMs. With this technique we are able to locally cause swelling and porosity changes in the PEM films, and use our method to qualitatively study the evolution of the porous film morphology. This technique has the potentially to locally control chemical functionality, film thickness, and mechanical properties, leading to a new ability to control film architectures both at the film surface and within the bulk of the film. Beyond the simple patterning technique, we believe that this technique will allow for a number of applications. Creation of metal nanoparticles in selected regions is easily demonstrable, and localized swelling makes for films with patterned regions that allow for cells to adhere differently.
5:15 PM - JJ7.8
Activation Energy from Gradient Zone Annealing of Block Copolymer Thin Films.
Alamgir Karim 1 , Gurpreet Singh 1 , Brian Berry 2
1 Polymer Engineering, University of Akron, Akron, Ohio, United States, 2 Chemistry, Univ. of Little Rock, Little Rock, Arkansas, United States
Show AbstractWe investigate the "cold - below ODT" thermal zone annealing (CZA)of block copolymer thin films and determine an Activation Energy of the ordering process. By comparing it to equivalent ordering in a static uniform oven annealing we see a sharp reduction of the Activation Energy under CZA conditions. By conducting 3D rotational SANS and reflectivity on the thin film samples we ascertain that the ordering occurs throughout the interior of the thin film sample. These measurements are conducted for a variety of thermal gradient profiles and speed of CZA under a hot wire profile. The synergy of CZA and block copolymer ordering on graphoepitaxy substrates which act as static ordering field will be reported as well as on soft confining substrates.
5:30 PM - JJ7.9
Extending Patterning Capabilities of Three-dimensional Nanostructures Generated by Proximity Field Nanopatterning.
Junyong Park 1 , Eunhye Kim 1 , Seokwoo Jeon 1 2
1 Materials Science and Engineering, Korea Advanced Institute of Science and Technology (KAIST), Dajeon Korea (the Republic of), 2 KAIST Institue for Nanocentury, Korea Advanced Institute of Science and Technology (KAIST), Daejeon Korea (the Republic of)
Show AbstractProximity field nanopatterning (PnP) offers a route to fabricate various three-dimensional (3D) nanostructures using elastomeric and conformable phase masks in a single exposure step. Light passing through a transparent binary mask made of poly(dimethylsiloxane) (PDMS) with surface relief structures generates complex 3D intensity distribution in photopolymer. The height of relief structures defines phase shift condition at a given refractive index of mask and exposure wavelength, and the change of height offers optimized conditions for generating diversified porosity and shape of 3D structures. However, experimental and modeling results from different phase shift conditions and the phase shift effect above π phase shift condition in the proximity field regime have not been confirmed. Also, fabrication of high-aspect-ratio relief structures without any collapse using PDMS is very limited due to its low modulus.In this work, Si masters to mold phase masks whose relief depths are ranged from 100 nm to 3 μm are prepared by ICP-RIE, which has been impossible to be achieved from normal masters with the relief structures composed of photoresists. Defect-free replication of high-aspect-ratio micropillars from masters is accomplished using high-modulus polyurethane (PU), and various back supporting substrates like polycarbonate (PC) films, slide glasses, and s-PDMS are optimized as imprinting molds or phase masks. For fully understanding the phase shift effect in the proximity field regime, the change of diffraction efficiencies at π/4 ~ 2π phase shift conditions is carefully measured, and the resulting 3D structures from those conditions are compared with experimental and computational work. The patterning results can give us another options to generate more sophisticated nanostructures at a given mask geometry such as duty cycle and dot to dot distance.Also, some of recent work for extending patterning capabilities with azopolymer and systemic analysis of optical transmission behavior from multi-dimensional nanostructures, potentially applicable to antireflection coating, will be introduced.
5:45 PM - JJ7.10
A Simple One Step Surface Modification Method for Graphoepitaxial Assembly of Block Copolymers.
Eungnak Han 1 , Padma Gopalan 1
1 , UW-Madison, Madison, Wisconsin, United States
Show AbstractWe present a new approach that can control the lateral orientation of perpendicular lamellae on a topographic pattern with homogeneous chemical modification. Instead of controlling each component namely the interfacial interaction of PS-b-PMMA with the sidewall and the trench bottom independently, we have focused on the thickness dependence of the microdomain orientation. When the interfacial interaction between the substrate and each block of PS-b-PMMA is in the vicinity of but not equal to the nonpreferential wetting conditions, microdomain orientation depends on the film thickness. This allows us to align perpendicular lamellae along the trench sidewalls by using homogeneous chemical modification of the topographic features. Hence by simultaneously controlling the thickness of the BCP film and the interfacial interactions we can dictate the right boundary conditions. We further show that on these chemically homogeneous surfaces we can laterally align perpendicular lamellae not only inside the trench but also on the mesa which increases the density of patterned lines when compared those created on a chemically heterogeneous topographic pattern.