Guihua Yu, Univ of Texas-Austin
Haiqing Lin, SUNY Buffalo
Ho Bum Park, Hanyang University
BM7.1: Charged Membranes for Water Purification
Monday AM, November 28, 2016
Hynes, Level 2, Room 202
8:00 AM - *BM7.1.01
Ion Solubility, Diffusion, Permeation and Conductivity in Charged Polymers
Benny Freeman 1
1 University of Texas at Austin Austin United StatesShow Abstract
Charged polymer membranes are widely used for water purification applications involving control of water and ion transport, such as reverse osmosis and electrodialysis. Efforts are also underway worldwide to harness separation properties of such materials for energy generation in related applications such as reverse electrodialysis and pressure retarded osmosis. Additional applications, such as energy recovery ventilation and membrane-assisted capacitive deionization, rely on polymer membranes to control transport rates of water, ions, or both. Improving membranes for such processes would benefit from more complete fundamental understanding of the relation between membrane structure and ion sorption, diffusion and transport properties in both cation and anion exchange membrane materials. Ion-exchange membranes often contain strongly acidic or basic functional groups that render the materials hydrophilic, but the presence of such charged groups also has a substantial impact on ion (and water) transport properties through the polymer.
We are exploring the influence of polymer backbone structure, charge density, and water content on ion transport properties. Results from some of these studies will be presented, focusing on transport of salt, primarily NaCl, through various neutral, positively charged and negatively charged membranes via concentration gradient driven transport (i.e., ion permeability) and electric field driven transport (i.e., ionic conductivity). One long-term goal is to develop and validate a common framework to interpret data from both electrically driven and concentration gradient driven mass transport in such polymers and to use it to establish structure/property relations leading to rational design of membranes with improved performance.
Ion sorption and permeability data were used to extract salt diffusion coefficients in charged membranes. Concentrations of both counter-ions and co-ions in the polymers were measured via desorption followed by ion chromatography or flame atomic absorption spectroscopy. Salt permeability, sorption and electrical conductivity data were combined to determine individual ion diffusion coefficients in neutral, cation exchange and anion exchange materials. Manning’s counter-ion condensation models and the Mackie/Meares model were used to correlate and, in some cases, predict the experimental data.
8:30 AM - BM7.1.02
Facile Construction of Anion Exchange Membranes with 3D Interconnected Ionic Nano-Channels by the Self-Organization of Polymerizable Ionic Liquid
Xinpei Gao 1 , Liqiang Zheng 1
1 Key Laboratory of Colloid and Interface Chemistry Shandong University Jinan ChinaShow Abstract
Anion-exchange membranes (AEMs) for alkaline fuel cells have triggered great interest in the energy field because of their distinct advantages in terms of enabling the use of non-precious metal catalysts, better oxygen reduction kinetics and fuel flexibility. However, the current AEMs often suffer from low OH− conductivity and poor chemical stability. Among the various strategies to improve the hydroxide ion conductivity, construction of a microphase separated morphology composed of hydrophilic ion nanochannel and a hydrophobic phase has been demonstrated as the most important strategy. Although several trials to construct microphase separated membranes using block copolymers, comb-shaped polymers, and graft polymers have been reported, achieving membranes with highly ordered and well-defined ionic nano-channels is still challenging.
The uses of molecular self-assembly to create nanostructured liquid-crystalline (LC) materials with highly ordered and well-defined ionic channels has been shown to be good candidates for efficient ion transportation. In particular, bicontinuous cubic liquid crystals are of considerable interest because of their 3D interconnected and well-defined periodical channel networks. The fixation of LC nanostructures within a polymeric film provides a considerate solution to achieve simultaneous enhancement of many required AEM properties. In this talk, our recent studies will be presented regarding the facile construction of AEMs with LC nanostructures via the self-assemble of polymerizable ionic liquids. Hexagonal, lamellar and bicontinuous cubic LC samples were prepared by the self-organization of polymerizable amphiphilic imidazolium-based ionic liquids. And for the first time, AEMs with hexagonal, lamellar and bicontinuous cubic nanostructures were fabricated through in-phase photopolymerization of liquid crystals. The AEMs performance in terms of ionic conductivity, hydration behavior, and chemical stability were characterized, which turned out to be closely related with the LC nanostructures retained after photopolymerization.
8:45 AM - BM7.1.03
Adhesive Interaction of Polyzwitterion Brushes Containing Inverse Phosphorylcholine Group
Motoyasu Kobayashi 1
1 Kogakuin University Tokyo JapanShow Abstract
Methacrylate monomer having an inverse phosphorylcholine at the side chain (MiPC) was synthesized by N,N-dimethylaminoethyl methacrylate, 2-chloro-2-oxa-1,3,2-dioxaphospholane, and isopropanol with 25% yield. Surface-initiated atom transfer radical polymerization of MiPC was carried out in methanol at 50 °C for 2 h to give poly(MiPC) brush with a 110 nm thick (dry state) on silicon wafer. The resulting poly(MiPC) was water soluble, however, the surface free energy was estimated to be 40.8 mN m-1 by Owens-Wendt method based on a water contact angle of 71 degree. When the poly(MiPC) brush was immersed in water, the thickness of brush increased from 110 to 171 nm due to the swelling of brush and hydrophilicity of poly(MiPC). Adhesion force of poly(MiPC) brush in water was also measured to be 30 nN by force curve measurement using a propylsilane-modified silica probe (d = 20 mm), indicating that poly(MiPC) brush has a relatively large hydrophobic interaction in spite of its hydrophilicity.
9:00 AM - BM7.1.04
Water-Polymer Distribution and Mobility in Hydrated Aromatic Ionomers under Confinement
Shudipto Dishari 1 3 , Christopher Rumble 1 , Mark Maroncelli 1 , Joseph Dura 2 , Michael Hickner 1
1 The Pennsylvania State University University Park United States, 3 Chemical and Biomolecular Engineering University of Nebraska–Lincoln Lincoln United States, 2 National Institute of Standards and Technology Gaithersburg United StatesShow Abstract
The response of ionomer thin films and bulk membranes to humidity is distinctly different. Hydration of fuel cell ionomers in supported thin films leads to complex multimodal interactions among water, polymer chains and substrate and these interactions may lead to interesting mechanical and transport properties. However, the properties of ionomers in thin film format are still not well understood. This understanding is crucial to explore the properties of the ionomer-catalyst interface of fuel cell electrodes. In this work, thin films of sulfonated aromatic ionomer, S-Radel were investigated to know how thickness and hydration lead to changes in density, water-polymer distribution and mechanical properties. A fluorescent rotor probe was incorporated into the polymer films (~25-250 nm thick) to predict the stiffness of the films using time resolved fluorescence. The density values obtained from quartz crystal microbalance and spectroscopic ellipsometry showed a similar trend with thickness to those obtained from neutron reflectometry. A ~25 nm thick film had lower density as compared to a ~250 nm thick film which corroborated with greater mobility and lower stiffness of thinner film observed at dry state. When the same sample was hydrated, film density and interfacial water volume fraction significantly increased. A very thin pure water layer was found at the substrate interface of the ~25 nm thick sample from neutron reflectometry. On the other hand, thicker films were less water-rich at the interface as compared to thinner samples. The water distribution near substrate interface in the aromatic s-Radel films was distinctly different from that in fluorocarbon based Nafion films seen in previous work. Antiplasticization, or stiffening of the films upon hydration, was observed at different extents from fluorescence lifetime of rotor probes. The plasticization properties appeared to be controlled by film thickness, film density, and water mobility.
9:15 AM - BM7.1.05
Exploration of Zwitterionic Hydrogels for Desalination and Energy Production from Salt Waters by Mechanical Stress
Sui Zhang 1 2 , Rohit Karnik 1
1 Mechanical Engineering Massachusetts Institute of Technology Cambridge United States, 2 Chemical and Biomolecular Engineering National University of Singapore Singapore SingaporeShow Abstract
Salty waters (e.g., seawater) are important sources for drinkable water production through various desalination technologies, such as reverse osmosis and distillation. Meanwhile, salinity gradients between two solutions of different concentrations offer great potential for renewable energy production, which has been demonstrated by pressure retarded osmosis (PRO) as well as other processes. However, challenges exist for both desalination and osmotic energy production, such as insufficient energy efficiency, serious fouling and relatively high costs, etc.
Alternative routes to achieve desalination or energy production from salty waters remain interesting to the community; one possible approach is by mechanical stress. Hydrogels are a group of materials that might respond differently to the changes in salt concentration or mechanical stress. For example, charged hydrogels absorb both ions and water when immersed in salt solutions and may release solutions with lower concentration upon application of mechanical stress, thereby achieving desalination; they also change their volume towards different salt concentration, which can be utilized to produce energy if mechanical stress is applied. In this study, we chose zwitterionic hydrogels because of their hydrophilic, super water-absorbing properties and their outstanding anti-fouling capability. Fundamental understanding on the structure-swelling-mechanical strength behaviors will be provided, and the potential of such hydrogels for desalination and energy production will be explored and discussed.
10:00 AM - *BM7.1.06
Ion Containing Block Copolymers for Emerging Energy Applications
Carl Willis 1
1 Kraton Polymers Houston United StatesShow Abstract
In 2010, Kraton Polymers started producing a grade line of ion containing, styrenic block copolymers under the tradename of Nexar(R) Polymers. The polymers are made by a 3 step process. In the first step, a 5 block copolymer is prepared by a living anionic polymerization technology - sequential addition of 1) t-butylstyrene, 2) isoprene, 3) styrene, 4) isoprene, and finally, 5) t-butylstyrene; the living anionic polymerization method affords polymer segments that are nearly monodispersed in molecular weight. In the second step of the synthesis, the isoprene segments are selectively hydrogenated to remove the C=C unsaturation. In the final step, the pentablock copolymer is selectively sulfonated in the polystyrene segment (center block).
The sulfonated polystyrene segment in these polymers gives the material unique structure and unusual performance features. Solutions of these polymers tend to be structured. In non-polar solvents, spherical micelles are formed with the ion microphase in the core of the structure. In polar solvents, spherical micelles are also formed but have the ion microphase on the outside of the micelle. Under some conditions with mixtures of polar and non-polar solvent blends, a different species is formed that has been hypothesized to be of a vesicle nature. Due to the structured nature of these polymer solutions, they have interesting rheological features.
The Nexar Polymer solutions have been cast into membranes which have found utility in energy recovery ventilation applications. By running fresh air over one side of the membrane and spent air over the other side of the membrane, water vapor can be transferred from on air stream to the other. In this way, humidity can be regulated in the incoming air stream with the result that the air can be conditioned at a substantially reduced cost. Regulation of humidity in the conditioned air can improve comfort, as well.
The Nexar Polymer solutions have also been printed onto fabrics and the resulting coated fabrics made into garments that provide an improved micro-climate for the wearer. This technology provides a mechanism for cooling the person wearing the garment when working in a hot climate.
At present, we are developing methods for spray coating these polymers onto porous and irregularly spaced surfaces - microporous membranes and various carbon powder coated structures.
Ongoing research is addressing opportunities for these polymers in water transport and water treatment applications. Various energy storage and energy generation applications are being examined, as well.
This presentation will focus on the science that supports these technologies.
10:30 AM - BM7.1.07
Self-Cleaning Membranes from Comb-Shaped Copolymers with Photoresponsive Side Groups
Papatya Kaner 1 , Xiaoran Hu 1 , Samuel Thomas 1 , Ayse Asatekin 1
1 Tufts University Medford United StatesShow Abstract
We introduce a new self-cleaning, photoresponsive membrane that can remove pre-deposited foulant layers upon exposure to UV light, exhibit UV-triggered surface morphology changes, and sustain stable pore size and permeance throughout. We first synthesized novel comb-shaped graft copolymers at two side-chain lengths with polyacrylonitrile (PAN) backbones and photoreactive side-chains using atom transfer radical polymerization (ATRP). The side-chains undergo a light-induced transition between a hydrophobic spiropyran (SP) state and a zwitterionic, hydrophilic merocyanine (MC) state, allowing photo-regulated control over membrane features. We used these comb-shaped copolymers to produce thin film composite (TFC) membranes by coating a commercial PVDF membrane with a thin layer of the copolymer solution. Changes in fingerprint IR peaks pertinent to SP and MC forms upon light treatment confirm the structural difference between the two forms at a molecular level. Prior to any photo-treatment, as-coated membrane surface consists mainly of hydrophobic SP groups, which promote the adsorption of hydrophobic solutes on pore channel walls, reducing flow rate. Upon reversing the photochemical response by irradiation with UV light, the SP groups are converted to hydrophilic MC groups that release the adsorbed molecules and permit water passage once again. This “self-cleaning” behavior is shown by measuring pre- and post-UV water permeability after fouling with model protein bovine serum albumin (BSA). We found that flux decline through a BSA-fouled membrane can be fully recovered back to its original value by a simple, non-mechanical intervention of exposure to UV light. In addition, despite the as-coated membrane, the UV-induced MC form membrane surface is fouling resistant, indicated by zero flux decline after two hours of protein filtration. To better understand how polymer self-organization controls the responsive behavior, the light-induced changes in surface topography and hydrophilicity are analyzed.
10:45 AM - BM7.1.08
Inverse Opal-Templated Multiscale Architectured Nanomembranes with Tunable Separation Properties
Pil Jin Yoo 1
1 Chemical Engineering Sungkyunkwan University Suwon Korea (the Republic of)Show Abstract
Membrane has been used from time immemorial to purify water. Advances made in membrane technology for more than a century have to do with either enhancing separation efficiency of the membrane or improving the permeation flux. Enhancing the separation efficiency, however, inevitably led to reducing the permeation flux, and improving the permeation flux resulted in a loss in the separation efficiency. This inherently built-in dilemma has to be dislodged for the filtration membrane to fully reach its potential. In this presentation, we suggest multiscale porous membranes that allow for high permeation flux without sacrificing separation efficiency. In order to create the multiscale architectured membranes, primary structure is first prepared by assembling closely packed colloidal particles, filling the gaps with a suitable material, and dissolving out the particles to form inverse opal structure. Then, secondary nanostructures are incorporated inside the structured template to elaborately tune the pore size, tortuosity, and interfacial properties. Embedded nanostructures can be created by layer-by-layer assembly of polyelectrolyte multilayers, microphase separation of block copolymers, or self-assembly of another colloidal particles, etc. Finally, the constructed multiscale architectures are utilized for water-treatment applications, such as ultrafiltration of nanoparticles or nanofiltration of metallic ions. Due to the perfectly ordered characteristics of the multiscale architecture, it offers advantages of reduced tortuosity as well as pore size uniformity, resulting in high permeability and selectivity simultaneously.
1) D. K. Rhee, B. Jung, Y. H. Kim, P. J. Yoo, ACS Appl. Mater. Interfaces 6, 9950-9954 (2014).
2) Y. M. Lee, B. Jung, Y. H. Kim, W.-S. Choe, P. J. Yoo, Adv. Mater. 26, 3899-3904 (2014).
3) Y. H. Kim, H. Kang, S. Park, D. Y. Ryu, P. J. Yoo, Adv. Mater. 26, 7998-8003 (2014).
4) G. H. Choi, F. Caruso, P. J. Yoo, ACS Appl. Mater. Interfaces 8, 3250-3258 (2016).
11:00 AM - BM7.1.09
Fabrication of Hierarchically Porous Membranes by Photofluidization of Azopolymers for Oil/Water Separation
Hong Suk Kang 1 , Shu Yang 1
1 University of Pennsylvania Philadelphia United StatesShow Abstract
Access to clean water and separation of oil/water mixtures have become urgent global issues due to the increased incidents of oil spills, water contamination, and water shortage. Separation oil/water via membranes with selective oil/water absorption is a relatively recent development. While simple oil/water mixtures can be separated by gravity, separation of surfactant stabilized oil/water emulsions is especially challenging. Meanwhile, to enhance selectivity of the membrane, smaller nanopores are preferred; while to achieve high permeation flux, micropores are preferred. Therefore, it is highly desirable to create a membrane with precisely controlled, hierarchical pores over a large area in a simple yet efficient way. Here, we utilize photofluidization of electrospun fiber network from azopolymer (polydisperse orange 3, PDO3), to fine-tune the pore size ranging from nano- to micron-scale. It is well known that azopolymers can undergo trans- to cis- isomerization under irradiation by visible light; even below the glass transition temperature (Tg), the polymer chains can move around, leading to photofluidization. This nature of azopolymers is caused by the repeated photo-isomerization of azobenzene molecules attached to the main chain of the polymer and their resulting anisotropic alignment in the direction perpendicular to the light polarization. First, we fabricate the microporous membranes by electrospinning of the azopolymers. Subsequently, we partially melt the fiber scaffold to shrink the pore size far below micron level by controlling the laser (l = 532 nm) irradiation time. Lastly, we demonstrate that the fabricated membranes can be utilized to separate submicron-sized water-in-oil emulsions with high separation efficiency (> 99.95 %).
11:15 AM - BM7.1.10
Influence of Nanoparticles on Phase Segregated Morphology of an Immiscible Polymer Blend Thin Film
Anuja Das 1 , Rabibrata Mukherjee 1
1 Indian Institute of Technology Kharagpur Kharagpur IndiaShow Abstract
Over the recent years, nanoparticle filled polymeric systems have attracted significant interest due to the fact that addition of such particles can drastically change the properties of the polymers, along with imparting its own functionality. In this regard, nanoparticle filled polymer blend thin film is getting greater attention as it has tremendous potential when implemented using functional polymer in the field of bulk heterojunction solar cells (BHJ). Unlike a homopolymer thin film, a polymer – polymer blend thin film on spin coating forms a laterally phase segregated morphology instead of smooth flat film. The effect of addition of nanoparticles on the phase-segregated morphology and on the stability of such systems is highly complex compared to its homopolymer counterparts and involves a richer physics as it deals with additional polymer–polymer interfaces. Hence, we present here a fundamental study on influence of addition of nanoparticle in the two-phase region of a polymer blend thin film.
With this work, we investigate the influence of organic nanoparticles on a phase-segregated morphology of a spin casted immiscible polymer blend on a flat substrate. For this fundamental study, poly(styrene) (PS) - poly(methylmethaacrylate) (PMMA) were chosen as immiscible polymers and fullerene (C60) as the organic nanoparticle (NPs). PS and PMMA being UCST blends, phase segregates at room temperature. Atomic Force Microscope images of ascast PS-PMMA blend reveals that on addition of nanoparticles, the lateral phase segregation of the domains reduces. From our initial experiments it was observed that on increasing the concentration of NP, lateral phase segregated domains reduces gradually. Moreover, beyond a critical concentration (Cn-NP*), the phase segregation was completely arrested leading to a flat film. By ellipsometric studies, thickness of the polymer blend with nanoparticle before and after selective phase removal hinted vertical phase separation instead of a typical lateral phase separation. Hence, from the results we qualitatively understand that the nanoparticles while spin coating, migrates towards the polymer–polymer interfaces and impart stability to the interface, thereby arresting the lateral phase segregation process during the latter stages of spin coating. This interfacial stability led to a vertical phase segregation of the PS and PMMA forming a polymer–polymer bilayer. This study can help us build a technique that is fast, simple yet novel to obtain coatings of multifunctional polymers.
Keywords: Polymer Blend, Thin Film, Phase Segregation, Nanoparticles, Fullerene, Thin Film Coatings, Interfacial Stability.
11:30 AM - BM7.1.11
Zwitterionic Random Copolymers for Next-Generation Membranes—Self-Assembly for Pore Size Control, Fouling Resistance and Molecular Imprinting
Ayse Asatekin 1
1 Tufts University Medford United StatesShow Abstract
Zwitterionic groups, defined as functional groups with equal numbers of positive and negative electrostatic charges, strongly resist biomacromolecular adsorption due to their high degree of hydration. This has led to their incorporation into membranes to prevent fouling by various methods, especially by grafting from and surface functionalization of existing porous membranes. In addition, however, zwitterionic groups have interesting self-assembly capabilities due to their high dipole moments and strong intra- and inter-molecular interactions. Our group aims to better understand how zwitterion-containing amphiphilic copolymers self-assemble, and utilize their behavior to develop membranes with improved capabilities: controlled, monodisperse pore size, controlled selectivity, high flux, fouling resistance, and scalable manufacture. We have prepared high flux, fouling resistant, size-selective membranes whose selective layers are made of random copolymers of zwitterionic and hydrophobic monomers. We have shown that within certain composition ranges, these copolymers self-assemble to form bicontinuous networks of nanochannels that allow water passage, and filter out solutes larger than the channel size. Membranes made by coating a thin layer of these copolymers onto a porous support exhibit fluxes as high as 21 L/m2.h.bar, which can be further be improved by better coating methods. Based on the rejection of anionic and neutral dyes of varying sizes, they show size-based selectivity with a cut-off around 1 nm. This pore size closely matches the size of the zwitterionic nanochannels, measured to be ~1.3 nm in diameter by transmission electron microscopy (TEM). These membranes also exhibit exceptional fouling resistance, showing little to no flux decline and essentially complete flux recovery with a water rinse upon the filtration of foulants such as protein solutions and oil suspensions. Well-designed membranes show no flux decline even in week-long fouling experiments with oil suspensions. This resistance arises from the presence of chemically dissimilar domains (hydrophobic and zwitterionic) of ~1 nm size, which frustrates the adsorption of foulants such as proteins. Furthermore, molecular imprinting approaches can be used to control and alter the selectivity of these membranes, further expanding their potential applications. These are the first examples of membranes that gain their selectivity from the self-assembled nanostructure of zwitterionic groups, in addition to exploiting this functionality for fouling resistance. These membranes are highly promising for a wide range of applications, including energy-efficient separations in the chemical and biochemical industries and industrial wastewater treatment.
BM7.2: Nanostructured Membranes for Separation
Ho Bum Park
Monday PM, November 28, 2016
Hynes, Level 2, Room 202
1:30 PM - *BM7.2.01
Polymers of Intrinsic Microporosity (PIMs)—High Free Volume Polymers for Energy-Efficient Separations
Peter Budd 1
1 University of Manchester Manchester United KingdomShow Abstract
Polymers of intrinsic microporosity (PIMs) are glassy polymers which possess high free volume and high internal surface area as a consequence of their relatively rigid, contorted macromolecular backbones. They comprise fused ring sequences interrupted by spiro-centres or other sites of contortion. PIMs have a high affinity for gases such as carbon dioxide, and for small organic species. The first commercial application of a PIM is in a sensor developed by 3M that acts as an end-of-life indicator for vapour-adsorbing cartridges. PIMs are being investigated as adsorbents and membrane materials for a variety of industrial separation processes, including gas separations (e.g., carbon dioxide capture) and organophilic liquid separations (e.g., bioalcohol recovery). For membrane gas separation, PIMs contributed to the revision of the upper bounds of performance by Robeson in 2008. For the practical application of high free volume polymers such as PIMs in membrane processes, the most significant issue to address is that of physical ageing, which leads to a reduction in permeability over time.
In recent years there has been significant research on PIMs aimed at tailoring selectivity, enhancing permeability and improving the ageing behaviour. This includes (1) new polymer synthesis, (2) chemical post-modification of precursor polymers, (3) thermal or ultraviolet treatment of membranes, (4) formation of polymer blends and (5) the addition of inorganic materials, carbons (activated carbons, nanotubes, graphene), metal-organic frameworks or purely organic materials, to form mixed matrix membranes.
2:00 PM - *BM7.2.02
Surface Patterning Polymeric Membranes for Improved Antifouling Performance
Yifu Ding 1 , Sajjad Maruf 1 , John Mersch 1 , Melissa Rickman 1 , Masoud Aghajani 1 , Alan Greenberg 1
1 University of Colorado at Boulder Boulder United StatesShow Abstract
Surface roughness of membranes is often perceived by many as a factor that promotes fouling during filtration, and thus is undesirable. Almost all liquid-based separation membranes have surfaces that are flat on the macroscale with local intrinsic surface roughness that is associated with the membrane manufacturing process. In this presentation, we show that surface patterns, i.e. engineered roughness, on membrane surfaces can improve their fouling resistance during microfiltration (MF), ultrafiltation (UF), nanofiltration (NF) and reverse osmosis (RO) processes. We will describe the underlying mechanisms and the corresponding processing-structure-performance relationships for surface patterning of different types of membranes. Comprehensive experimental studies reveal that the presence of the surface patterns significantly improved the overall filtration productivity and regeneration characteristics of the patterned membranes, in comparison to that of non-patterned controls, during separation of model suspensions of colloids and protein as well as salt solutions. Based on fluid mechanics modeling studies, the enhancement in performance was attributed to pattern-enhanced fluid shear.
2:30 PM - BM7.2.03
High Performance Polyethers for Membrane CO2/N2 Separation
Junyi Liu 1 , Haiqing Lin 1
1 State University of New York at Buffalo Buffalo United StatesShow Abstract
Carbon capture and sequestration (CCS) could be an important approach to mitigate CO2 emissions to the atmosphere. Membrane technology has been widely explored for CO2 capture from coal power plant derived flue gas, due to its low cost and high energy-efficiency. The key to the success of this technology is membranes with high CO2 permeability and high CO2/N2 selectivity. The current leading materials for membrane CO2/N2 separation are poly(ether oxide) (PEO) containing polymers, because ether oxygens can interact favorably with CO2, leading to high CO2 sorption and permeability. Given the enormous flow rate of the flue gas, any improvement in CO2/N2 separation properties can significantly decrease the cost of CO2 capture. The goal of this work is to design and synthesize a series of new polymers containing higher content of ether oxygens than PEO to improve CO2 permeability and CO2/N2 selectivity. More specifically, we have synthesized poly (1, 3 dioxolane) (PDXL) with different molecular weights of 510 g/mol and 1005 g/mol with a ratio of oxygen to carbon of 0.67, which is higher than that in PEO (0.5). These PDXL oligomers were also functionalized with acrylate groups and were thoroughly characterized using NMR, MS and FTIR. These oligomers were then polymerized by photo-polymerization and the resulting polymers were characterized for gas sorption and permeation. These new polyethers have demonstrated their promise for membrane CO2/N2 separation. For example, PDXL (n=5) derived polymer exhibits CO2/N2 selectivity of 82 with CO2 permeability of 100 Barrers at 35oC. The CO2/N2 selectivity is much higher than that of crosslinked PEO analogues (with CO2/N2 selectivity of 52). This presentation will also report fundamental solubility and diffusivity of other gases such as ethylene and ethane in these polymers.
2:45 PM - BM7.2.04
3-Dimensional Silica as a Multi Porous Support for Amine Loaded Carbon Dioxide Capture
Christopher Cogswell 1 , Sunho Choi 2
1 Chemical Engineering Northeastern University Boston United States, 2 Chemical Engineering Northeastern University Boston United StatesShow Abstract
Solid sorbents for carbon dioxide capture have many benefits, including high diffusion rates and surface areas, but also suffer from low capture capacities and selectivity for carbon dioxide. One popular method to overcome this challenge is to load amines onto the solids, through physical impregnation or covalent attachment to surface groups. While these materials can show high capacities with enough amine content, there is a tradeoff that exists between the kinetics of capture and amine loading, because the pores where amine is impregnated into the support are often the only channel available for gas diffusion. To overcome this challenge we have begun investigating sorbents that contain multiple pore channels which can be preferentially loaded with amines via size selection, allowing for a material which contains high contents of amine groups but still retains fast diffusion speed. One material, known as 3-Dimensional Disordered Silica, is composed of agglomerated spheres of zeolite beta that when loaded with polyethylenimine show fast capture kinetics and high capacities. We have shown that this material can be preferentially loaded in either the micropores present within spheres, or mesopores between spheres, allowing for an increased control of the pore-amine interaction and resulting capture performance.
3:00 PM - BM7.2.05
From Highly Crystalline to Outer Surface-Functionalized Covalent Organic Frameworks—A Modulation Approach
Mona Calik 1 , Torben Sick 1 , Florian Auras 1 , Thomas Bein 1
1 University of Munich Munich GermanyShow Abstract
Covalent organic frameworks (COFs) represent an emerging class of crystalline, porous materials exhibiting unique structural and functional diversity. By combining multidentate building blocks via covalent bonds, two- or three-dimensional frameworks with defined pore size and high specific surface area can be constructed. Crystallinity and porosity are of central importance for many properties of COFs, including electronic transport. Here, we present a new method for strongly enhancing both aspects through the introduction of a modulating agent in the synthesis. The competition between the bridging COF building block and the terminating modulation agent influences the dynamic equilibrium during framework formation, slowing down the COF growth and supporting the self-healing of crystal defects. Under optimized conditions, the crystal domains of COF-5 reach several hundreds of nanometers. The obtained materials feature fully accessible pores with an internal surface area of over 2000 m2 g-1.
Compositional analysis via NMR spectroscopy revealed that the COF-5 structure can form over a wide range of boronic acid to catechol ratios, spanning from highly boronic acid-deficient frameworks to networks with catechol voids.
Using functionalized modulators, this synthetic approach also provides a new and facile method for an external surface functionalization of COF domains, providing accessible sites for post-synthetic modification reactions.
We anticipate that the realization of highly crystalline COFs with the option of additional surface functionality will render the modulation concept beneficial for a range of applications such as gas separation, catalysis, and optoelectronics.
 A. P. Côte, A. I. Benin, N. W. Ockwig, M. O'Keeffe, A. J. Matzger, O. M. Yaghi, Science 2005, 310, 1166-1170.
 M. Calik, F. Auras, L. M. Salonen, K. Bader, I. Grill, M. Handloser, D. D. Medina, M. Dogru, F. Löbermann, D. Trauner, A. Hartschuh, T. Bein, Journal of the American Chemical Society 2014, 136, 17802-17807.
 M. Calik, T. Sick, M. Dogru, M. Döblinger, S. Datz, H. Budde, A. Hartschuh, F. Auras, T. Bein, Journal of the American Chemical Society 2016, 138, 1234-1239.
3:30 PM - *BM7.2.06
Mixed-Matrix Membrane Containing Aligned Montmorillonite for Carbon Dioxide Separations
Michael Guiver 1 2 , Zhihua Qiao 3 2 , Song Zhao 3 2 , Zhi Wang 3 2
1 State Key Laboratory of Engines Tianjin University Tianjin China, 2 Collaborative Innovation Center of Chemical Science and Engineering Tianjin China, 3 Chemical Engineering Research Center Tianjin University Tianjin ChinaShow Abstract
Mixed-matrix membranes composed of highly CO2-permeable montmorillonite aligned layers interspersed with polyvinylamineacid was bonded onto porous polysulfone membrane substrates. High-speed gas transport channels are formed by aligned interlayer gaps of the modified montmorillonite, through which CO2 transport primarily occurs. A high CO2 permeance is achieved combined with high mixed CO2-gas pair selectivity that is stable over time, independent of water content in the feed.
4:00 PM - BM7.2.07
Regenerable Mesoporous MgO Calcined from Metal Organic Frameworks (MOFs) for CO
Zelong Xie 1 , Christopher Cogswell 1 , Dinara Andirova 1 , Sunho Choi 1
1 Chemical Engineering Northeastern University Boston United StatesShow Abstract
Carbon capture and storage (CCS) technology has been gaining more attention due to considerable correlation between atmospheric carbon dioxide concentration and global climate changes.1,2 Among many potential methods and materials for CO2 Capture, alkaline earth-based oxide materials such as calcium oxides and magnesium oxides have emerged as one of the promising solid sorbent materials owing to their advantages such as wide availability of precursors in nature, low cost and low toxicity.3,4
CO2 capture by metal oxides follows the exothermic reaction: MO(s)+CO2(g)↔MCO3(s), where M can be alkaline metals including Mg, Ca, Sr and Ba. Specifically, magnesium oxides have been widely studied mainly because of their lower energy requirement for regeneration compared to calcium oxides.3
However, owing to the mediocre CO2 adsorption capacities and the large capacity decrease at high temperatures caused by the formation of a nonreactive surface layer of carbonate which affects all metal oxides, there must be actions taken to enhance the efficiency of MgO absorbents. Currently, there are two methodologies for MgO performance enhancements: one of them is the impregnation and wet mixing of K2CO3 and other alkaline metals with MgO which resulting in better CO2 adsorption capacity and remarkable regeneration5; another method is synthesis of porous MgO as a more desirable sorbent due to its high surface area and narrow pore size distribution.6
In this work, we focus on the synthesis and CO2 adsorption performances of mesoporous magnesium oxide nanoparticles synthesized via thermal decomposition of metal organic frameworks (MOFs). For instance, a Mg(BDC) MOF is hydrothermally synthesized and used as a precursor to create MgO nanoparticles via calcination. Characterization techniques such as X-ray diffraction, SEM, TEM, IR and BET surface area analysis were employed to access the structural information of MgO nanoparticles, while their CO2 adsorption characteristics were analyzed using TGA at different adsorption and desorption temperatures. More details about the roles which different calcination temperatures and heating rates play in terms of CO2 capacities and regenerability, as well as the possible explanations for good regenerability will be discussed.
 C. F. Cogswell, H. Jiang, J. Ramberger, D. Accetta, R. J. Willey, and S. Choi, Langmuir, 2015, 31, 4534−4541.
 D. Andirova, C. F. Cogswell, Y. Lei, S. Choi, Micropor. Mesopor. Mat., 2016, 219, 276–305.
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 S. C. Lee, B. Y. Choi, C. K. Ryu, Y. S. Ahn, T. J. Lee, J. C. Kim, Environ. Sci. Technol., 2008, 42, 2736–2741.
 S. Bian, J. Baltrusaitis, P. Galhotra and V. H. Grassian, J. Mater. Chem., 2010, 20, 8705–8710.
4:15 PM - BM7.2.08
Engineering Hydrophobic Organosilica Doped Nanofibers for Enhanced and Fouling Resistant Membrane Distillation
Mohamed Amen Hammami 1 , Jonas Croissant 1 , Lijo Francis 2 , Noreddine Ghaffour 2 , Shahad Alsaiari 1 , Niveen Khashab 1
1 Smart Hybrid Materials Laboratory, Advanced Membranes and Porous Materials Center King Abdullah University of Science and Technology Thuwal Saudi Arabia, 2 Water Desalination and Reuse Center, King Abdullah University of Science and Technology King Abdullah University of Science and Technology Thuwal Saudi ArabiaShow Abstract
Engineering and scaling-up new material for better water desalination is imperative to find alternative fresh water sources to meet future demands. Here, the fabrication of polyetherimide (PEI) composite nanofiber membranes doped with novel periodic mesoporous organosilica (PMO) nanoparticles comprising ethylene-pentafluorophenylene bridges is reported. The results showed an increase in hydrophobicity that is propertional to the percent of PMOs in the composite membranes. Direct Contact Membrane Distillation (DCMD) experiments were carried out for a comercial polytetrafluoroethylene membrane, PEI, and PEI-PMO doped nanofiber membranes. PEI nanofiber membranes showed more than 100% flux improvement compared to the comercial membrane. PMO doping of only 5%, showed a further increase of flux by ~140% compared to commercial membrane. Quantitative studies showed that bacterial adhesion on the engineered PEI-PMO nanofiber membrane has reduced by 40% due to the low surface energy of the embeded hybrid nanoparticles and the surface roughness of the composite nanofibers . The high porosity of PMO nanoparticles was further utilized to load an antimicrobial agent, namely Eugenol, showing a dramatic enhancement in the anti-biofouling properties of the electrospun nanofiber membrane where ~70% reduction of the bacterial attachment was noted after 24 hours .
4:30 PM - BM7.2.10
Polymeric Desiccants with High Adsorption Capacity and Low Regeneration Temperature for Energy-Efficient Cooling
Shuang Cui 1 , Patrick Charles 1 , Renkun Chen 1
1 University of California, San Diego La Jolla United StatesShow Abstract
Residential and commercial buildings consume a large amount of energy in cooling. About 45% of energy consumption is related to building temperature regulation through air conditioning (AC) and the demand for AC load is estimated to be increased by 6.2% annually. Therefore, it is appealing to develop alternative cooling technologies to assist or even substitute the conventional vapor compression (VC) cooling systems, especially for hot and humid climate with high latent heat load. Solid desiccant cooling (SDC) is one of the promising technologies because it can separately treat latent and sensible heat loads by pre-dehumidifying the moist air with desiccants, leading to high coefficient of performance (COP). Moreover, SDC systems are environmental friendly as it does not use chlorofluorocarbon refrigerants and is compatible with low-grade thermal energy, e.g., from solar or waste heat, for desiccant regeneration. The performance of SDC systems is hinged on the characteristics of the desiccants, most notably the adsorption capacity and the regeneration temperature. Typical desiccants exhibit either high adsorption capacities (e.g. ~2 g/g for polymeric desiccants with regeneration temperature of 80-100 oC ) or low regeneration temperatures (e.g. 40-57 oC for natural rock-based composite desiccants with adsorption capacities of ~ 0.2 g/g ), but it has been difficult to simultaneously achieve high absorption capacity with relatively low regeneration temperature. Here, we synthesized a novel desiccant, which shows both high adsorption capacity (~2 g/g) and low regeneration temperature (~ 40-50 oC) for the first time, by impregnating hygroscopic salts into a polymer matrix. Our thermodynamic modelling and experimental work further showed that the COP of SDC systems based on this novel desiccant can be enhanced by 3-fold, which is promising for energy saving and greenhouse gas emission reduction from building cooling.
BM7.3: Poster Session I: Nanostructured Polymers for Energy Application
Ho Bum Park
Monday PM, November 28, 2016
Hynes, Level 1, Hall B
8:00 PM - BM7.3.01
Effects of Molecular Structure on the Thermal and Mechanical Properties of Electrospun Vinyl Polymer Nanofibers
Yin Zhang 1 2 , Qian Zhang 1 , Xin Zhang 1 , Yunfei Chen 2 , Leon Bellan 1 , Richard Mu 3 4 , Deyu Li 1
1 Department of Mechanical Engineering Vanderbilt University Nashville United States, 2 Jiangsu Key Laboratory for Design and Fabrication of Micro-Nano Biomedical Instruments, School of Mechanical Engineering Southeast University Nanjing China, 3 Center for Physics and Chemistry of Materials Fisk University Nashville United States, 4 TIGER Institute Tennessee State University Nashville United StatesShow Abstract
Polymers are an important class of materials because of their desirable and tunable properties, abundance and low-cost. The properties of individual polymer nanofibers can be significantly different from those of the corresponding bulk, especially when the orientation and crystallinity of the molecular chains in the nanofibers are carefully tuned. For example, it has been shown that polyethylene (PE) nanofibers can possess thermal conductivities that are orders of magnitude higher than the bulk value. As such, it is important to characterize the microstructure and physical properties of polymer nanofibers to establish structure-property relations, which may help identify the key factors that dominate the properties and provide guidance when engineering the properties of a polymer for a specific application.
We have measured the thermal conductivities and Young’s moduli of three kinds of vinyl polymer nanofibers, i.e., polyvinylidene fluoride (PVDF), polyvinyl alcohol (PVA) and polyvinyl chloride (PVC), fabricated by electrospinning. These fibers have the same backbone, composed of carbon-carbon bonds, with only one or two atom differences in each monomer. The molecular orientation and crystallinity of individual nanofibers was carefully characterized using polarized micro-Raman spectroscopy. To characterize the physical properties of individual nanofibers, we used a thermal bridge method with suspended microheaters/thermometers to extract the thermal conductivities and the well-established three-point bending method to characterize the Young’s modulus with an atomic force microscope.
Our results show that in addition to the molecular chain orientation, the molecular composition and structure can also have important effects on the thermal transport properties. Among the measured fibers, PVA has the highest thermal conductivity and PVC has the lowest thermal conductivity with PVDF in the middle. It is also worth noting that all these fibers have a thermal conductivity much lower than that of electrospun PE fibers. We attribute the difference in the measured thermal conductivities to the composition and structure of the monomers, the basic building block of polymers. Lighter atoms on the side chains do not significantly alter the carbon atom vibrational modes and allow phonons to propagate without much disturbance, leading to high thermal conductivity. On the other hand, heavy atoms on the side chains may significantly change the vibrational modes to reduce the thermal transport capability. Similarly, the observed Young’s modulus of PVA nanofibers is higher than that of PVDF nanofibers, which correlates with the measured thermal conductivity trend.
8:00 PM - BM7.3.02
Understanding the Shape Memory Behavior of Thermoplastic Polyurethane Elastomers with Coarse-Grained Molecular Dynamics Simulations
Md Salah Uddin 1 , Jaehyung Ju 1 , Nandika D'Souza 1
1 University of North Texas Denton United StatesShow Abstract
We perform molecular dynamics (MD) simulations to understand thermally triggered shape memory behavior with an enhanced coarse-grained (CG) model of a thermoplastic polyurethane (TPU) elastomer. Hard and soft phases of shape memory polymers (SMPs) are known as fixed and reversible phase, respectively. Fixity depends on the content of hard segments due to their restricted mobility. On the contrary, recovery depends on the dynamic motion of the soft segments as well the degree of cross-linking, which is also affected by the quantity of hard segment. Several CG models of the TPU are constructed varying the weight percentage of soft segments to observe their effects on shape recovery and fixity. All of the models are equilibrated at 300K (above glass transition, Tg: 200-250 K) and deformed under uniaxial loading with NPT (isothermal-isobaric) ensembles. The deformed state is cooled to 100K (below Tg) and further equilibrated to estimate the shape fixity. Shape recovery is predicted by heating and equilibrating the structures back to 300K. By the end of this study, we may answer how much the shape fixity and recovery are changed for varying concentration of soft segments from thermomechanical cycles with CGMD simulations.
8:00 PM - BM7.3.03
Anisotropic Self-Assembly of Bare/Polymer Grafted Nanoparticle Blends in Homopolymer
Kishore Kumar Sriramoju 1 , Venkat Padmanabhan 1
1 Indian Institute of Technology Kharagpur IndiaShow Abstract
Molecular dynamics simulations are used to investigate the self assembly of a mixture of bare and polymer grafted nanoparticles in a polymer melt. The nanoparticles are modeled as spherical beads, polymers and grafted chains as bead-spring chains. Addition of grafted particles to polymer/(bare) particle blends results in the self assemble of bare particles into different anisotropic structures ranging from spherical to cylinders to branched cylinders. In all systems, the grafted nanoparticles attach to the surfaces of bare particle clusters due to depletion attraction. The rate of addition of bare nanoparticles to the cluster is higher than the rate of grafted particles. Finally, the minimization of the system energy results in the formation of different nanoparticle morphologies. At intermediate graft densities, the effective graft density of each individual bare nanoparticle cluster increases, as a result steric repulsions between the clusters increases, which leads to the formation of more number of small spherical clusters. For higher graft densities, the grafted particles are dispersed and separated from the bare cluster, which leads to the formation spherical clusters by the bare particles. These systems undergo structural transitions due to the interplay of grafted chain length, graft density and concentration of grafted particles. The structural map obtained by this study provide insights into how the geometric characteristics of the cluster can be tuned to achieve experimentally desired structural behavior. Our results indicate a possibility of formation of anisotropic structures with bare nanoparticles in polymer nanocomposites and offer flexibility in the design of new smart materials like chemical sensors, light emitting devices and photonics.
8:00 PM - BM7.3.05
Ordered Mesoporous Crystalline Aluminas and Composites from ABC Triblock Terpolymer–Directed Self-Assembly
Kwan Tan 2 1 , Ulrich Wiesner 2
2 Materials Science and Engineering Cornell University Ithaca United States, 1 Low Energy Electronic Systems IRG Singapore-MIT Alliance for Research and Technology Singapore SingaporeShow Abstract
Thermally stable and periodically ordered mesoporous ceramic and ceramic–carbon composite materials are appealing for use in various high temperature catalysis, separation, and energy related applications. We describe a one-pot synthesis approach to generate ordered mesoporous crystalline γ-alumina–carbon composites and ordered mesoporous crystalline γ-alumina materials via the combination of soft and hard templating chemistries using block copolymers as soft structure-directing agents. Periodically ordered alumina hybrid mesostructures were generated by self-assembly of a poly(isoprene)-block-poly(styrene)-block-poly(ethylene oxide) terpolymer, butanol and aluminum tri-sec-butoxide derived sols in organic solvents. The triblock terpolymer was converted into a rigid carbon framework during thermal annealing under nitrogen to support and preserve the ordered mesoporous crystalline γ-alumina–carbon composite structures up to 1200 °C. Subsequently the carbon matrix was removed in a second heat treatment in air to obtain ordered mesoporous crystalline γ-alumina structures.
8:00 PM - BM7.3.06
Boosting the Performance of Self-Assembling Random Zwitterionic Copolymers Using Ionic Liquids during Membrane Formation
Prity Bengani-Lutz 1 , Ayse Asatekin 1
1 Tufts University Medford United StatesShow Abstract
Polymer self-assembly is a promising tool for scalable manufacture of membranes while maintaining high permeability and controlled pore size. Tuning copolymer composition (monomers, additives) and processing methods can change copolymer behavior which can dramatically affect the self-assembly and hence the membrane performance (permeability, selectivity, fouling resistance). Studies based on block copolymers demonstrate the influence of additives (solvent, homopolymer etc.) on the copolymer self-assembly and membrane performance. But studies on additives in casting solutions of random copolymers and how they affect membrane performance have not been reported to our knowledge. Recently, we have introduced a new class of membranes with ~ 1 nm effective pore size whose selective layers are made of self-assembling zwitterionic amphiphilic random copolymers. These membranes derive not only their excellent fouling resistance but also their permeability and selectivity from this self-assembled nanostructure. These membranes have numerous applications in the biochemical and pharmaceutical industries, as well as wastewater treatment processes. These membranes are prepared simply by coating random copolymers of hydrophobic and zwitterionic monomers onto a porous support membrane. In this study, we have used ionic liquids and other additives in the coating solutions to boost and alter the performance of these membranes. Membranes prepared by coating copolymer solutions with sufficient amounts of selected additives on commercial ultrafiltration membrane supports exhibit permeances as high as 50 L/m2.hr.bar, up to 10 times higher than membranes formed without additives. These membranes also exhibit a narrow pore size distribution, retaining the same size-based selectivity with a ~1 nm size cut-off demonstrated by filtering negatively charged dyes. Performance of these membranes depends on the amount of additive as well as the membrane manufacturing method (non-solvent, drying time etc.). This is attributed to phase separation and solvent diffusion kinetics that are in play during membrane formation. These new membranes with high fluxes and sharp selectivity are promising for various applications such as textile wastewater treatment, pharmaceutical purification and bioseparation applications.
8:00 PM - BM7.3.07
New Shear Thickening (‘Dilatancy’) Dispersion Based on Nano-Silica Beads
Temperature-Dependence and Concentration Rheology
Abeer Olayan 1 2 , Alfredo Alexander-Katz 2 , Jason Cox 1
1 Saudi Aramco Dhahran Saudi Arabia, 2 Massachusetts Institute of Technology Cambridge United StatesShow Abstract
A highly innovative Shear Thickening Fluid (STF) was developed based on nano-silica particles. These particles have the ability to form a highly viscous gel at high shear/high temperature conditions. The inspiration of this innovation was taken from the medical industry mimicking the dynamic of biopolymers in a blood clotting cascade. The concept of the new STF is based on the introduction of short and long polymers grafted randomly onto silica particles. By inserting a hydrophobic functional group in a short polymer chain with hydrophilic macromolecules (silica with a long polymer chain) that will aggregate in water when the fluid experiences high shear rates (such as when passing through a drill bit). The remarkably strong hydrogen bonding resulting from high shear and high temperature provides a significant increase in fluid viscosity.
The gelling behavior of the material under shear and temperature should offer significant advantages in different application in Oil and Gas operation such as: drilling, well control and EOR. At the low shear rates encountered, the fluid is a low-viscosity, pumpable liquid. Yet as it passes through well, the resulting high shear rates cause the fluid to thicken either reversibly or permanently into a high-strength viscous fluid depending on the application.
8:00 PM - BM7.3.08
Dynamic Self-Assembly of Polyrotaxane Thermoplastic Elastomer
Rina Maeda 1 , Shuntaro Uenuma 1 , Koichi Mayumi 1 , Hideaki Yokoyama 1 , Kohzo Ito 1
1 University of Tokyo Chiba JapanShow Abstract
Dynamic self-assembly is one of the most important tools to give living cells the biological functions such as sensing of external environment, cellular movement, and division. In contrast to static self-assembly, dynamic self-assembly could be deformed or reformed by kinetic control, which indicates it has a tremendous potential to be utilized for novel energy-function converting materials and complicated modulation of the material functionalities. However, there have been few reports on the functional materials that utilized the dynamic self-assembling system.
Currently, we are focusing on designing thermoplastic elastomers that can change their self-assembled structure and physical properties in responsive to the applied mechanical stimuli utilizing polyrotaxane. Polyrotaxane is a family of supramolecules with a topological characteristic, in which many cyclic molecules are threaded onto a single polymer chain capped at both chain ends with bulky end-groups. It is easily imagined that the cyclic compoinds can be freely sliding when the mechanical stimuli are applied.
The polyrotaxane was newly synthesized from poly(ethylene glycol) (PEG) and α-cyclodextrines (CDs) functionalized with trimethylsilyl groups. It was found that the CDs stacked parallel to the elongated direction of the polyrotaxane film with a d-spacing of 1.3 nm. The cylindrical rigid rod structure formed by stacked CDs was determined to form a hexagonally packed cylindrical structure with a d-spacing of 1.7 nm using wide-angle X-ray diffraction analyses. Furthermore, the cylindrical structures found to form a periodic domain with a d-spacing of 40 nm by applied mechanical stimuli, which was determined by small angle X-ray scattering analyses. It can be considered that the ring components slid along the PEG axis polymer chain to form a periodic rigid rod hard domains with the mechanical force is applied. This drastic morphological change was coupled to the physical properties revealed by dynamic viscoelasticity measurements.
We promise the new thermoplastic elastomer designed based on novel concept open a much wider window for materials of which functionalities can be precisely modulated by external mechanical stimuli.
8:00 PM - BM7.3.09
Supported Metallocene onto Sphere-Morphological Mesoporous Material Contained Montmorillonite for Polymerization of Ethylene
Yu Kang 1
1 Beijing Research Institute of Chemical Industry, SINOPEC Beijing ChinaShow Abstract
At present, metallocene catalysts have attracted worldwide attention for the polymerization of ethylene because of their excellent catalytic performance [1~4]. In the case of polymerization in slurry, the metallocenes can be supported on some mesoporous silicate materials. The investigation revealed that the external morphology of mesoporous materials was the major factors to influence their practical applications [6–8]. Therefore, the kind of mesoporous material contained montmorillonite with sphere-like morphologies was successfully prepared via spray-drying method for the first time. Such mesoporous material was applied as the support to immobilize metallocene for the homopolymerization of ethylene and copolymerlzation of ethylene/1-hexene.
The kind of sphere-like shape catalyst was synthesized according to analogous procedures reported [9~12]. Such mesoporous material was applied as a support to immobilize metallocene ((n-BuCp)2 ZrCl2 and MAO) with the Al content of 24 % (wt) and Zr content of 0.6% (wt) (from (XPS)). The texture, structure and morphology of material were characterized by power XRD, SEM, TEM, and N2 adsorption. XRD and TEM result showed that the catalyst remained mesoporous structure. SEM results indicate that the sphere-like shape morphology of mesoporous materials remained even after metallocene loading. The mean partical diameter of the material was analyzed by laser particle size analyzer. The catalytic performance of supported catalysts was studied systemically for polymerization of ethylene. The results revealed that the supported catalyst could remain the initial morphology and microstructure of mesoporous support materials, and presented uniform pore size distribution.
In summary, the kind of sphere-like shape mesoporous material contained montmorillonite supported by metallocene has been synthesized from a spray-drying synthesis approach successfully. And the catalyst showed superior catalytic properties for homopolymedzation and copolymenzation of ethylene/1-hexene to the commercial catalysts using silica gel.
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8:00 PM - BM7.3.10
Colloidal Crystallization and β-Phase Transformation of Poly(Vinylidene Fluoride) Nanoparticles
Daichi Okada 1 , Yohei Yamamoto 1
1 Pure and Applied Sciences University of Tsukuba Ibaraki JapanShow Abstract
Poly(vinylidene fluoride) (PVDF) is one of representative fluoropolymers, and their unique piezo-, pyro-, and ferroelectric properties are utilized for versatile applications such as sensors, memories, actuators, power storage. PVDF primarily forms three types of chain conformation in the crystalline state: α-phase with a trans-gauche+-trans-gauche– (tg+tg–) conformation, β-phase with an all-trans conformation, and γ-phase with an intermediate state of α- and β-phases (tttg+tttg–). Among these, β-phase PVDF exhibits ferroelectric properties due to its unidirectional polarization. However, the most thermodynamically stable conformation is α-phase. Therefore, methodology for the β phase transformation is a key issue for utilizing PVDF as ferroelectric materials.
Recently, fluoropolymer nanoparticles (NPs) are produced and utilized for enhancing the electronic properties of materials. For example, by an addition of polarized fluoropolymer NPs into the active layer of π-conjugated polymer photovoltaics, the charge separation is accelerated while the charge recombination is efficiently suppressed.
In our research, we focus our attention on PVDF NPs, and attempt a construction of colloidal crystals from the PVDF NPs. Colloidal crystals have attracted a lot of interests because of their simple fabrication process to construct 3D periodic structures. Most polymeric colloidal crystals studied thus far consist of optically and electrically inert polymers such as polystyrene (PS) and poly(methylmethacrylate) (PMMA). If colloidal crystals are constructed from ferroelectric polymers, novel photonic properties can be expected such as confinement of higher-order harmonics into colloidal crystals.
The obtained PVDF NPs with an average diameter of 230 nm mostly form α-phase, which is consisted of 46% α-phase and 54% amorphous PVDF. Firstly, the PVDF NPs were assembled on a quartz substrate by means of vertical deposition method from a tetrahydrofuran (THF) dispersion of PVDF NPs with a few volume percentage of n-alkane that is higher b.p. than THF. The resultant colloidal thin films displayed a pale-greenish structural color with the selective reflection at around 550 nm wavelength due to closely packed PVDF NPs. Furthermore, The fabricated PVDF colloidal thin films has particular angular dependence of selective reflectance to colloidal crystals. The fabricated colloidal thin films were then immersed into an acetonitrile solution containing 2 wt% ionic liquid, subsequently air-dried, and thermally annealed at 140 °C, just below the melting point of the PVDF-IL blends. After annealing, the PVDF NPs partially transformed into its β phase with the volume percentages of α-, β- and amorphous phases of 22, 32, and 46%, respectively. The post-annealed colloidal films still maintained the periodic fcc assembling structure of PVDF NPs, thus displaying the greenish structural color and selective reflection.
8:00 PM - BM7.3.11
Combined Ionic and Hydrogen Bonding in Polymer Multilayer Thin Film for High Gas Barrier and Stretchiness
Chungyeon Cho 1 , Jaime Grunlan 1
1 Texas Aamp;M University College Station United StatesShow Abstract
The possibility of stretchable gas barrier nanocoating was studied with an all-polymer multilayer using layer-by-layer assembly. Electrostatically-bound polyethyleninmine (PEI)/polyacrylic acid (PAA) and hydrogen bonding-based polyethylene oxide (PEO)/PAA layers were incorporated into four interbonding layers in which PAA serves as a bridging molecule. Assembly pH had a direct effect on the film’s growth and structure. With all layers deposited from pH 3 aqueous solutions, a densely packed multilayer thin film was formed with relatively high gas barrier, achieving an oxygen transmission rate (OTR) 15 times lower than the 1 mm thick polyurethane (PU) rubber substrate. At 10% strain, the film becomes more oriented and densified (reducing free volume), resulting in a significant improvement in OTR (28 times lower than uncoated PU rubber). When stretched between 10 and 50%, an OTR that is 7 to 8 times lower than the substrate was maintained. This unique, stretchable coating, along with its excellent gas barrier properties, would make possible to expand the horizon of applications for elastomeric objects and electronic packaging applications, many of which are used in energy generation and medical devices.
8:00 PM - BM7.3.12
Preparation and Characterization of Polyethylene Glycol/Polyvinyl Alcohol Composite Nanofibers
Xi Luo 1 , Chaoming Wang 1 , Linan An 2 1
1 Southwest Jiaotong University Chengdu China, 2 Department of Materials Science and Engineering University of Central Florida Orlando United StatesShow Abstract
Along with the continuous deepening research on nanofibers, the applications of fibers are no longer limited to the textile industry, and also show a wide range of application prospects in civil, medical, military, and other fields. Although there are many kinds of methods to prepare nanofibers, the electrospinning is one of the most popular and convenient method. Compared with other methods, the fibers made by electrospinning have large specific surface area, controllable diameter, strong structural stability, and other properties. In this work, polyethylene glycol/polyvinyl alcohol (PVA/PEG) phase change composite nanofibers were prepared by using a self-designed electrospinning device at ambient temperature. The diameter, morphology, composition, thermal and mechanical properties of PVA/PEG nanofibers were studied by scanning electron microscopy (SEM), Fourier transform infrared spectrometer (FT-IR), differential scanning calorimetry (DSC), atomic force microscopy (AFM). The SEM results showed that the electrospinning effect became worse with the increase of the content of PEG. DSC studies shows that PVA increased the thermal structural stability of PEG. According to AFM measurement, it was proved that additive PEG reduced the Young's Modulus of the composite fibers compared with the pure PVA fibers.
8:00 PM - BM7.3.13
Sustainable Cylindrical Water Triboelectric Nanogenerator Based on PTFE Nanolayered Surface
Jihoon Chung 1 , Sukyung Lee 1 , Sangmin Lee 1
1 School of Mechanical Engineering Chung-Ang University Seoul Korea (the Republic of)Show Abstract
A triboelectric nanogenerator (TENG), a renewable energy technology to efficiently harvest mechanical energy into electrical energy, has elicited worldwide attention because of its cost-effectiveness and sustainability. This device utilizes contact electrification which is induced by friction between two dielectrics with triboelectric polarity to produce electricity from wasted mechanical energy. Recently, the TENG was developed using water-solid contact electrification, which used water as dielectric itself and significantly reduced the friction damage between two materials. In this study, we developed a cylindrical water triboelectric nanogenerator which controls the water flow by fabricating patterned hydrophobic/-philic surface with polytetrafluoroethylene (PTFE) nanolayer. As a first report, this study demonstrates new design of fully packaged water-solid contact TENG, called cylindrical water triboelectric nanogenerator (CW-TENG), which has a complete packaged design to generate multiple output in single rotation through patterned surface. CW-TENG can be integrated with multiple generating hydrophobic/-philic generating units in single TENG device without occupying extra space for installation. Furthermore, this study is the first to demonstrate possibility of using hydrophilic surface as additional energy harvesting device as well as water reservoir in a packaged design. Until now, hydrophilic surface was only considered as incompatible element for TENG because water volume on the hydrophilic surface remains after the first contact. The rotating design pushes water on the hydrophilic surface constantly to force the water volume change to induce electrical potential difference between two surfaces. In addition, this study demonstrates analysis of the electrical energy generation by water volume change on the hydrophilic surface with computational dynamic simulation. The electrical potential difference between water and the electrode is shown to increase as the water volume change is increased. Utilizing this new result and analysis, various TENG design using hydrophilic surface can be developed for practical use. In this design, the super-hydrophobic surface TENG generates open-circuit voltage (VOC) of 7 V and closed circuit current (ICC) of 50 nA, and hydrophilic surface TENG can produce VOC of 2 V and ICC of 60 nA. With more super-hydrophobic and hydrophilic patterned electrode inside this device, the total power generated by the device is estimated to be multiplied. Thus, with this research will provide a potential solution of energy harvesting using water flow and self-powered system.
8:00 PM - BM7.3.14
Designed Synthesis of Stable, Porous, and Functionalized Organic Microporous Polymers
Yingjie Qian 1 , Minjae Kim 1 , Jaeil So 1 , Sang Eun Shim 1
1 Chemistry and Chemical Engineering INHA University Incheon Korea (the Republic of)Show Abstract
Organic microporous polymers are at the front line in the field of advanced material science due to their interesting chemical, physical, and optical properties arising from tremendous monomers and various synthesizing routes. Among diverse synthesizing strategies, we prefer to choose two methods to carry out our experimental. First is Sonogashira coupling reaction. Second is Schiff base reaction. Sonogashira coupling reaction is relatively matured method to couple two molecules by eliminating halogen (I or Br) and proton bonded to alkyne from two different monomers. After careful polymerization, we could obtain high surface area (1000 m2/g) conjugated or tetrahedral structured polymers depending on monomer’s structures with protected alkyne group. As it known to all, polymers with alkyne allow us to post-treat it using click chemistry to obtain tri-azole which could lead to transition metal chelates. Even though Sonogashira coupling reaction has many advantages in synthesizing polymer it still faces an issue, homo-polymerization of alkyne monomer. In order to solve this problem we select Pd/TBAF catalysts instead of commonly used Pd/CuI. By adopting Pd/TBAF catalyst, we obtained ideally ordered polymer. In the case of the Schiff base, synthesized polymers containing amide group show high crystallinity and high surface area but are weak under aqueous condition including acidic and basic. In order to solve this problem, we will use electron donating-withdrawing properties of functional group to fortify the stability of the polymer under the aqueous conditions. We select the methoxy group as an electron donating group to abate the repulsive forces arising from the unequally distributed electron cloud densities commonly resulting in the unstable structure of the polymers. By using as synthesized polymers in our team, we tested its potential in the field supercapacitor, catalytic reactions, and so on.
This study was supported by the National Research Foundation of Korea (grant no.: 2015R1A4A1042434).
8:00 PM - BM7.3.15
Directed Self-Assembly of Block Copolymers in Thin Films on Topographically-Patterned Surface for Nanolithography
Dong-Eun Lee 1 , Jinwoong Kim 1 , SeongHo Park 1 , Dong Hyun Lee 1
1 Dankook University Yongin-si Korea (the Republic of)Show Abstract
Block copolymers (BCPs) composed of two or more chemically distinct polymer chains linked by covalent bonding can self-assemble into a variety of nanometer-scale domains including sphere, cylinder, and lamellae, which can become versatile platforms to fabricate well-defined nanostructures for potential applications. However, the self-assembly of block copolymers on flat surface inevitably meets imperfection like dislocation, and grain boundaries in ordering of the domains. These defects are currently regarded as major drawbacks that should be overcome to realize ultra-high density array of ordered nano-features in large area. Directed self-assembly (DSA) of block copolymers has often been used to generate long-rage ordering of BCP domains in thin films. But, conventional methods for DSA in BCP thin films are still limited due to several disadvantages that require complicated multi-step process, high cost templates and so on. In this study, we introduce an intuitive and effective method to achieve highly ordered nanostructures of block copolymers in thin films by using solvent-annealing process on polymer nano-stripes. The extremely aligned nano-stripes of poly(tetrafluoro ethylene) (PTFE) which has low friction coefficient and high wear rate were directly produced on various substrates (Si wafer, glass, and polymer films) by mechanically rubbing a PTFE bar. Then polystyrene-block-poly(2-vinylpyridine) copolymers (PS-b-P2VP) were subsequently spin-coated on the nano-stripes of PTFE and annealed in vapor of organic solvents to induce self-assembly of block copolymers. By adjusting solvent-annealing conditions, highly ordered BCP nanostructures which were oriented either vertically or horizontally to the surface were revealed in large area because of the guidance of underlying PTFE patterns. These well-ordered BCP nanostructures were utilized as either templates to synthesize inorganic nanodots or nanowires or etching masks for wet etching process.
8:00 PM - BM7.3.16
High-Performance Flexible Piezoelectric Nanogenerators Consisting of Porous Cellulose Nanofibril (CNF)/Poly(dimethylsiloxane) (PDMS) Aerogel Films
Qifeng Zheng 1 , Huilong Zhang 2 , Hongyi Mi 2 , Zhiyong Cai 3 , Zhenqiang Ma 2 , Shaoqin Gong 4
1 Materials Science Program University of Wisconsin-Madison Madison United States, 2 Electrical and Computer Engineering University of Wisconsin-Madison Madison United States, 3 Forest Products Laboratory U.S. Department of Agriculture Madison United States, 4 Biomedical Engineering University of Wisconsin-Madison Madison United StatesShow Abstract
There is a growing demand for renewable energy technologies due to the shortage of fossil energy resources and environmental concerns. Nanogenerators (NGs) that can harvest energy from ambient sources (e.g., mechanical vibration, heat, acoustic waves, and human activities) have attracted significant attention during the past decade. Piezoelectric materials, capable of generating electrical power from accessible and ubiquitous mechanical energy sources are the most promising candidates for developing NGs. Nevertheless, several factors including high cost of raw materials (e.g., ZnO nanowire or BaTiO3), and/or complicated fabrication procedures have limited their mechanical flexibility as well as their production scalability and ultimately, their potential applications. Thus, there is an ongoing pursuit for novel and cost-effective flexible piezoelectric materials that can be fabricated via simple and scalable processes while providing high output power and device flexibility.
Considering cellulose nanofibrils (CNF)’s excellent mechanical properties, chemical stability and relatively high piezoelectric coefficient (26–60 pC/N), flexible CNF-based aerogels hold great promise in the development of self-powered electronic systems including piezoelectric NGs. We recently develop a novel, simple, cost-effective, and scalable technique to fabricate high-performance flexible piezoelectric nanogenerators (NGs) using porous CNF/poly(dimethylsiloxane) (PDMS) aerogel film. The porous CNF/PDMS aerogel film was prepared by coating a layer of PDMS on the porous surface of a compressed CNF aerogel film produced via an environmentally friendly freeze-drying process. The porous CNF/PDMS aerogel film was then sandwiched between two thin PDMS films, followed by two aluminum foils, to form the flexible NGs. Under periodic external mechanical deformation by an oscillator, the resulting flexible porous CNF/PDMS aerogel film-based NGs exhibited very stable and high output piezoelectric signals; namely, an open-circuit voltage (Voc) of 60.2 V, a short-circuit current (Isc) of 10.1 μA, and a corresponding power density of 6.3 mW/cm3. The electric power generated by these NGs was able to directly turn on 19 blue light-emitting diodes (LEDs) and charge a capacitor up to 3.7 V. Furthermore, these NGs also demonstrated excellent stability, integratability and durability. Considering their excellent piezoelectric performance, ease of large-scale manufacturing, and environmental friendliness, this technology provides a promising solution for developing practical, flexible, and self-powered electronic devices.
8:00 PM - BM7.3.17
Direct Carbonization of 3D Polymer Patterns
Da-Young Kang 1 , Cheolho Kim 1 , Gyurim Park 1 , Jun Hyuk Moon 1
1 Sogang University Seoul Korea (the Republic of)Show Abstract
Three-dimensional porous polymer structure was fabricated by interference lithography. The direct carbonization of 3D nanostructure has attracted interest for obtaining 3D carbon materials. The polymer flow and subsequent change occur during high temperature treatment. Liquid immersion thermal treatment was applied to enhance the thermal resistance and maintain the structural integrity during high temperature treatment. The thermal crosslinking reaction of structured polymer pattern was characterized. The 3D polymer pattern successfully converted to 3D carbon pattern via liquid immersion thermal treatment. Structured carbon pattern was applied to the supercapacitor after nitrogen doping for pseudocapacitance. The liquid immersion heat treatment can be extended to the carbonisation of various polymer or photoresist 3D patterns and also provide a facile way to control the surface energy of polymer 3D patterns for various purposes, for example, to block copolymer or surfactant self-assemblies.
8:00 PM - BM7.3.18
Functional Hybrid Biomaterials Based on Organophosphorous Hydrolase
Christopher DelRe 1 , Ting Xu 1 2
1 University of California, Berkeley Berkeley United States, 2 Lawrence Berkeley National Lab Berkeley United StatesShow Abstract
Organophosphorus hydrolase (OPH) can efficaciously degrade harmful organophosphates (OPs), a class of acutely toxic neuro-inhibitory chemicals extensively employed as pesticides and chemical warfare agents. However, OPH tends to aggregate in aqueous solution, resulting in a significant decrease of its native activity within hours. Furthermore, there has been limited success in incorporating OPH into synthetic materials to fabricate smart fabrics or devices because most materials processing techniques require organic solvents, which denature the protein. Several groups have demonstrated that OPH can retain activity when exposed to organic solvents, but the techniques employed thus far have had limited success in generating effective OPH-based functional materials.
Inspired by natural chaperons, we have created a random heteropolymer comprising different chemical moieties with complimentary interactions to OPH – hydrophobic, hydrophilic, and negatively charged – to encapsulate and stabilize OPH in both aqueous and organic media. When complexed with the designed polymer, OPH demonstrates a drastic increase in biological activity in buffered aqueous solution – approximately 15 times greater than the native biological activity of pure OPH in the same environment. Additionally, the heteropolymer-OPH complex is soluble and remains active when stored in organic media (while pure OPH is insoluble in the same media). This allowed us to fabricate OPH-loaded electrospun nanofibers from a toluene/chloroform mixture using a wide range of polymers. Our OPH-loaded fibers displayed substantial biological activity in aqueous media as well as in organic solvents, providing a route for functional materials toward efficient large-scale degradation of these harmful OP chemicals.
8:00 PM - BM7.3.19
Generating Protein-Based Nanoassemblies via Statistically Random Copolymers and Block Copolymers
Brian Panganiban 1 , Izaac Sit 1 , Alisa Bowen 2 , Ting Xu 1 2 3
1 Materials Science and Engineering University of California, Berkeley Berkeley United States, 2 Chemistry University of California, Berkeley Berkeley United States, 3 Materials Sciences Division Lawrence Berkeley National Laboratory Berkeley United StatesShow Abstract
A bottom-up approach towards protein-based nanoassemblies has the potential to change the current paradigm of materials science. Synergistic integration of protein and synthetic block copolymer is of particular interest. A protein library rich in functionality coupled with a block copolymer’s ability to direct the assembly of nanoparticles into well-defined nanoscale structures has the potential to improve a variety of technological sectors. This includes biosynthetic catalysis, energy conversion, and molecular sensing. However, it still remains a challenge to preserve protein structure and function while making them readily processable. Proteins primarily reside in aqueous media and are typically not amenable for usage beyond biomedical applications. Conversely, amongst the numerous processing conditions required to fabricate materials, organic solvent-use generally remains a common necessity. A protein’s insolubility and inability to remain functional in non-aqueous solutions are significant hurdles that need to be addressed. Here, we show that through the development of rationally designed statistically random copolymers, it has become possible to stabilize proteins and process them in organic media. The chemical complexity offered by statistically random copolymers allows us to manipulate the interactions between protein, solvent, and block copolymer. Their amphiphilic nature and ability to multivalently hybridize with a protein’s surface enables protein-use far beyond the current scope of aqueous-based device fabrication and chemistry. After encapsulation in statistically random copolymer-based complexes, proteins are readily available for co-assembly with block copolymers. Proteins remain functional throughout the entire process, block copolymer microphase separation remains unhindered, and proteins are nanoscopically arranged in controllable hierarchical structures.
8:00 PM - BM7.3.20
Self-Assembly of Conjugated Polymers into Helical Nanostructures
Stephanie Fronk 1 , Guillermo Bazan 1 , Cheng-Kang Mai 1 , Martin Seifrid 1 , Yueqin Shi 1
1 University of California, Santa Barbara Santa Barbara United StatesShow Abstract
Chirality is universally present in nature and imparts specific functionality to organic and inorganic compounds. Introducing a chiral side-chain to donor-acceptor conjugated polymers results in self-assembly of helical aggregate nanostructures. The asymmetry of the side-chain influences the packing structure of the polymer chains in the aggregate and in the solid state. Adding a chiral side chain to a benzotriazole-thiophene copolymer results in self-assembly into a chiral aggregate. Circular dichroism (CD) spectroscopy reveals the expected bisignate Cotton effects in solution with solvents ranging from toluene to dichlorobenzene. CD response is obtained even at low solution concentrations (0.0025mg/mL) and when 90% of the material in solution contains racemic side chains and only 10% contains chiral side chains. The magnitude of the CD response is about one-tenth that of the purely chiral solution. The chiral organization translates from solution to the solid state. The difference in secondary structure with the substitution of chiral for racemic side chains provides a method for controlling the geometry of the aggregates. This control over aggregate geometry could prove beneficial in a variety of optoelectronic applications such as organic thin film transistors and sensors.
8:00 PM - BM7.3.21
Fabrication of Microporous Carbon Nanoparticles Caused by Conjugated Microporous Polymer Using Friedel-Craft Reaction for a Supercapacitor Electrode
Minjae Kim 1 , Yingjie Qian 1 , Sang Eun Shim 1
1 Chemistry and Chemical Engineering Inha University Incheon Korea (the Republic of)Show Abstract
The development of conjugated microporous polymers (CMPs) showed a unique possibility for high energy storage electrochemical supercapacitor. CMPs are classified as of microporous organic polymers (MOPs). CMPs have been extensively investigated for gas storage, controlled drug release, catalysis, and energy storage devices because of their low densities, chemical and thermal stability, permanent porosity, high specific surface area, pore volume, and regular pore size distribution. Specially, in supercapacitor system for high energy storage and fast charge-discharge performance based on its reaction mechanism, the material having high and regular pore structure have been needed. Recently, the activated carbon used at commercial supercapacitor market have been struggled to make a high energy storage device due to its irregular and isolated pore structure.
Herein, we demonstrate a facile strategy for the design and synthesis of triazine based microporous carbon nanoparticles (T-MCNs) having regular micro-pore structure as a high performance supercapacitor electrode. T-MCNs were fabricated using novel organic polymer synthesized simple Friedel-Craft method which was for the first time synthesized by cyanuric chloride and 1,3,5-triphenylbenzene in dichloromethane (DCM) under solvothermal condition at 70 oC using anhydrous aluminium chloride as a catalyst. After synthesis, the attained sample was carbonized in tubular furnace at 700, 800, and 900 oC with nitrogen and carbon dioxide atmosphere, respectively. T-MCNs carbonized at 800 oC (T-MCNs 800) as a supercapcitor electrode showed unique capacity behavior (418 F/g at 1 A/g) and excellent cycling stability (98 % retention after 1000 cycles at 1 A/g) in 6 M KOH aqueous electrolyte. Therefore, well designed T-MCNs through triazine based microporous polymer supplied promising prospect as new supercapacitor electrode material for substituting activated carbon.
This study was supported by the National Research Foundation of Korea (grant no.: 2015R1A4A1042434).
8:00 PM - BM7.3.22
Analysis of High Thermal Conductivity Mechanism of Side Chain Type Liquid Crystalline Methacryl Polymers with Odd Number of Spacer Carbons
Yuzo Itoh 1 , Kengo Ando 1 , Tadatomo Kawai 1
1 Kogakuin University Tokyo JapanShow Abstract
Recently, in the electrical and electric devices, such as motors in hybrid car, or PC and mobile phones with high performance and small sizes, the increase of the heat generated inside them has become severe problems. As insulating materials, epoxy polymer is typically used in these kind of devices, but the thermal conductivity of the epoxy polymer is small (around 0.2 Wm-1K-1), 1 to 3 orders smaller than those of metal or ceramics in general. The addition of filler increases of the thermal conductivity of epoxy polymer, but the viscosity also increases at the same time. Thus, the high thermal conductivity of the polymer itself is required
The liquid crystalline epoxy polymer which include twin mesogens, the twin-mesogen epoxy polymer has shown recently to have a relatively large thermal conductivity, five times larger than those of conventional epoxy polymers and such a large thermal conductivity of the liquid crystalline epoxy polymer has been explained qualitatively to come from its higher orderliness of liquid crystalline structure.
We also synthesized and analysed thermo-plastic liquid crystal polymers and found the methacryl polymers with biphenyl type mesogen show twice larger thermal conductivities than that of conventional methacryl polymer (PMMA).
In this work, we synthesized side chain type liquid crystalline methacryl polymers with spacer carbon numbers of 3,5 of which mesogen end group was methyl group and investigated the effects of high-order structure changes due to the difference of spacer carbon numbers and alkyl carbon numbers of the mesogen end group on the thermal conductivities. We will discuss the effects of even and odd spacer carbons and the alkyl chain length of end group of mesogen on the higher-order structure and the thermal conductivities of side chain type liquid crystal polymers.
8:00 PM - BM7.3.23
Structural and Thermal Characterization of High Thermal Conductivity Amorphous Polymers having Ionization-Induced Chain Extension
Chen Li 1 , Apoorv Shanker 2 , Gunho Kim 6 , Jinsang Kim 3 2 4 , Kevin Pipe 1 5
1 Mechanical Engineering University of Michigan, Ann Arbor Ann Arbor United States, 2 Macromolecular Science and Engineering University of Michigan Ann Arbor United States, 6 Department of Mechanical and Nuclear Engineering Ulsan National Institute of Science and Technology Ulsan Korea (the Republic of), 3 Department of Material Science and Engineering University of Michigan Ann Arbor United States, 4 Department of Chemistry University of Michigan Ann Arbor United States, 5 Department of Electrical Engineering and Computer Science University of Michigan- Ann Arbor Ann Arbor United StatesShow Abstract
Amorphous polymers (APs) generally act as thermal insulators, as their thermal conductivities (κ) are low, falling primarily within a narrow range of 0.1-0.5 Wm-1K-1 (compared to ~100s Wm-1K-1 for metals). Low-cost and scalable methods to increase thermal conductivity in APs would have significant impact in numerous industries, as applications range from electronics packaging to vehicle structures. Most previous efforts, however, have either limited practical scope (e.g., mechanical stretching) or greatly increased material cost (e.g., blending with high-κ fillers such as metal powders).
Here we present a means to tackle this challenge using a scalable and low-cost molecular engineering approach, utilizing charge repulsion forces between ionizable side groups in a polyelectrolyte (polyacrylic acid, PAA) to extend its backbone and hence promote the efficient flow of thermal (vibrational) energy. Using this method, we achieve a factor of six increase in κ for spin-cast thin films. The solution pH is used to control the degree of ionization in PAA (the fraction of carboxylic groups that ionize) and hence the backbone charge density, with which the extent of chain extension and thermal conductivity are positively correlated.
We apply a number of experimental techniques to characterize the physical properties that change upon PAA ionization and lead to the dramatic enhancement observed in thermal conductivity. Fourier transform infrared spectroscopy (FTIR) is used to quantify the degree of ionization (α) in the solid-state PAA films, where the height of the carboxylic group (COOH) peak relative to that of the ionized carboxylic group (COO-) peak is observed to continuously decrease as pH grows, suggesting a steady increase in α. To quantify backbone chain extension in the aqueous state, the PAA radius of gyration (Rg) is calculated by measuring the viscosity (η) of the PAA solution at various pH values, since Rg is related to η1/3 (as well as to molecular weight, which is kept constant) by the Flory viscosity constant. As PAA chains swell in solution, their enhanced viscosity translates into thicker films under identical spin-cast conditions, which we confirm by thickness data obtained via ellipsometry. We then use a differential 3ω technique to determine the cross-plane thermal conductivities of thin film samples both with and without an alumina capping layer (to block humidity), measuring similar κ values for both configurations. PAA films spin-cast from pH 1 to pH 10 solutions exhibit a continuously increasing trend in thermal conductivity (0.2 to 1 Wm-1K-1). Lastly, the amorphicity of PAA is verified by XRD, where the absence of prominent crystalline peaks excludes contributions to κ enhancement by polymer crystallization. Therefore, we establish the links between pH and chain extension (by FTIR), chain extension in solution and in solid-state (by viscosity and ellipsometry), and chain extension in solid-state and thin film thermal conductivity.
8:00 PM - BM7.3.24
Synthesis of Methacrylate Polymers That Have Spacer Carbon Number 2 or 6 and Alkyl Chain Length 6 of Mesogen, Phenyl Benzoate End Group and Analysis of Their High Thermal Conductivity Mechanism
Yuzo Itoh 1 , Norihisa Abe 1 , Tadatomo Kawai 1
1 Kogakuin University Hachiouji JapanShow Abstract
Recently, electrical machineries and apparatuses have become smaller and higher quality, and heat generated inside machineries causes overheating and various malfunction of these. Thus it is a serious problem how the heat is radiated and cooled. Generally, machineries have been cooled by radiator, but cooling efficiency of the insulating part in the machinery is very inefficient as thermal conductivity of polymers that were used to insulting material, is very low. It has been used to solve this problem that the inorganic fillers are added to the matrix conventional polymers of which thermal conductivities are very small. Thus we should add so much fillers that the necessary physical properties like low viscosity of the materials are lost. Therefore increase of the thermal conductivity of polymer itself is required.
The thermo-setting epoxy polymer is used generally for the insulating material. We investigated and found that the epoxy polymer which had twin mesogens showed liquid crystal structures and five times larger thermal conductivity than a conventional one.
Thermo-plastic polymer is better than thermosetting polymer, for example, in forming processability. Thus molded article made by thermoplastic polymer can be produced in large quantities easily. In this work, we synthesized thermoplastic side chain type liquid crystal methacrylate polymers that have spacer length 2 or 6 and end group, alkyl chain length 6 of phenyl benzoate as mesogen and analyzed their high thermal conductivity mechanism, comparing their thermal conductivities to those of side chain type liquid crystal methacrylate polymers with odd number spacer carbons and with methyl group as end group of mesogen. We will discuss the effects of even and odd spacer carbons and the alkyl chain length of end group of mesogen on the higher-order structure and the thermal conductivities of side chain type liquid crystal polymers.
8:00 PM - BM7.3.25
Synthesis and Molecular Weight Effect of
Polyurethane Covalently Grafted to Graphene Oxide
Kyung Seok Kang 1 , Chanhyuk Jee 1 , Min Jeong Park 1 , Eun Young Kim 1 , PilHo Huh 1
1 Department of Polymer Science and Engineering Pusan National University Busan Korea (the Republic of)Show Abstract
A series of thermoplastic polyurethane (TPU) based on poly(tetramethylene glycol) (PTMG 1000) as a polyol and methylene diphenyl diisocyanate (MDI) as a isocyanate were successfully synthesized on different formulation to evaluate the molecular weight (MW) effect. Graphene oxide (GO) sheets were chemically grafted with allophanate-functionalized TPUs. Mechanical properties and thermal properties of TPU/Graphene oxide (TPU-g-GO) nanocomposites were systematically estimated with adding the stoichiometric GO to TPU with different MW. Transmittance of individual TPU-g-GO were sequentially changed in the range from 79.72 to 90.15 %, with dependence of GO content. Water-barrier properties of TPU-g-GO nanocomposites was measured using water vapor transmission rate test. TPU-g-GO films would be extensively attracted for greatly potential possibility of high-performance films for electrical and electrochemical applications.
8:00 PM - BM7.3.26
Transparent and Hydrophobic Properties of Polyurethane Chemically-Incorporated to Polydimethylsiloxane
Chanhyuk Jee 1 , Kyung Seok Kang 1 , Min Jeong Park 1 , Eun Young Kim 1 , PilHo Huh 1
1 Pusan National University Busan Korea (the Republic of)Show Abstract
Polyether-polydimethylsiloxane (PDMS) polyurethane (PU) are successfully synthesized using three different molecular weights (= 550, 6000, 110,000) of siloxane polyol and one fixed molecular weight of polyethylene glycol (PEG) polyol as a soft segment. Wettability and surface properties of PDMS-PU are evaluated with respect to PDMS molecular weight and PDMS mol %. PDMS enrichment at the air-polymer interface could result from the phase separation effect between PDMS segments and urethane segments. Surface energy of PDMS-PU is decreased with increasing PDMS molecular weight and content. PDMS segments in PCDMS-PU attributes to high- or super-hydrophobic surface and high contact angle with water, which could lead to the potential water-barrier property. The optical transmittance and water vapor transmission rate of PDMS-PU are investigated to use as an encapsulation material for the environmental protection and industrial applications.
8:00 PM - BM7.3.27
Pre-Resonant Raman Spectra of Ordered Organic Polymers in Nano-Confinement
Steluta Dinca 1 , Damian Allis 1 , Michael Sponsler 1 , Bruce Hudson 1
1 Syracuse University Syracuse United StatesShow Abstract
We report here an experimental strategy for preparing polyacetyelene, (CH)x, as an array of stereoregular polyene chains constrained within the channels of a crystalline solid. The method we used to synthesize this composite/hybrid conjugated material is based on the solid-state polymerization of a reactive molecule (1,4-diiodo-1,3-butadiene, DIBD) constrained within a one-dimensional tunnel host (urea, CO(NH2)2) structure.
DIBD/urea single-crystals were grown by standard crystallization procedures, from a solution containing DIBD guest molecules, and urea dissolved in methanol (MeOH). Organo-iodine compounds like DIBD, when irradiated with either UV or visible light, undergo a homolytic breakage of the carbon-iodine bond to generate I-CH=CH-CH=CH● radicals and I● atoms; the I atoms, ultimately as I2, escape the urea matrix after photodissociation as determined by weight measurements. Such radical species are stable in isolation in the urea inclusion complexes. Two adjacent radicals can react to form the stable dimeric species IHC=CH-CH=CH-CH=CH-CH=CHI. Continuation of this process results in the production of tunnel-bound longer diiodopolyene.
Raman spectroscopy was used to probe the resulting conjugated polyene chains and to study the time dependence of the photoinduced polymerization in these crystals. We found that UV or broadband UV/visible radiation results in two strong and sharp resonance-enhanced Raman modes at 1121 and 1509 cm-1. A weaker non-resonant band at 1293 cm-1 was also observed; we used this line as an internal standard for “good” samples. The Raman spectra of the confined polyenes are very similar to that of known polyene species and to spectra of trans-(CH)x prepared by solution methods. A qualitative interpretation of these new Raman features as due to diiodopolyenes products will be discussed.
The kinetic evolution of the product polyene features exhibits three phases. Initially, there is an appearance of a very strong scattering near 1500 cm-1 and a second one with a relative lower intensity near 1100 cm-1, associated with C=C and C-C stretching deformations, respectively. This is followed by an increase in the intensity ratio I1100/I1500 with the 1100 cm-1 feature becoming dominat. Furthermore, during this time interval, the non-resonate polyene band near 1290 cm-1 is observed as well. The intensity of the 1290 cm-1 band is constant for most of the photochemical transformation, but eventually disappears at later times. The third phase of the kinetic process shows the progressive loss of Raman intensity for both of the two polyene bands with the 1100 cm-1 band being the last to disappear. This is the behavior expected as very long conjugated chains are produced.
1. A. E. Lashua, T. M. Smith, H. Hu, L. Wei, D. G. Allis, M. B. Sponsler, and B. S. Hudson, Cryst. Growth Des. 12, 3852 (2013).
2. H. Kuzmany, E. A. Imhoff, D. B. Fitchen, and A. Sarhangi, Phys. Rev. B, 26, 7109 (1982).
8:00 PM - BM7.3.28
Thermal Behavior and Chemical Composition of a Copolymer-Clay Nanocomposite Montmorillonite
M.I.C.A. Oscar Guerrero 1 2 , Bernardo F. Campillo 3 2 , Martha L. Patino 1
1 Universidad Autónoma del Estado de Morelos Mexico Mexico, 2 Instituto de Ciencias Fisicas Cuernavaca Mexico, 3 Facultad de Quimica Mexico MexicoShow Abstract
Today the incorporation of nano-clay in polymer matrixes greatly enhances the properties of the polymer. However, its application is extensive, such as coatings, auto parts, rubber stamps, and many others. In the present work, the thermal behavior and composition of a copolymer nanocomposite with Montmorillonite clay nanoparticles are discussed. The copolymer composition is composed of butyl acrylate (BA), styrene (STY), and methacrylic acid (MAA), and a Na montmorillonite nano-clay (MMT) was used. The nanoparticles are incorporated during the polymerization process (in-situ process). The state of chemical composition was performed by infrared spectroscopy (IR).The spectra showed that increasing the clay-nanoparticles it was observed an increment of Si-O incorporated in the copolymer matrix. Also, these nanocomposites retain their common optical transparency of an acrylic even increasing the concentration of MMT. In addition, the study of thermal gravimetric analysis (TGA), shows that the nanoparticles have a negative trend in thermal stability disregarding the copolymer matrix concentrations. It was also observed an increment in the glass transition temperature by differential scanning calorimetry.
8:00 PM - BM7.3.29
Thin-Film Morphologies and Templated Self-Assembly of High Molecular Weight Polystyrene-Block-Polydimethylsiloxane under Solvent Vapor Annealing
Li-Chen Cheng 1 , Wubin Bai 1 , Eduardo Fernandez 1 , Kun-Hua Tu 1 , Konstantinos Ntetsikas 2 , George Liontos 2 , Apostolos Avgeropoulos 2 , Caroline Ross 1
1 Massachusetts Institute of Technology Cambridge United States, 2 MSE University of Ioannina, University Campus-Dourouti Ioannina GreeceShow Abstract
Due to the thermodynamic incompatibility between different blocks of a block copolymer (BCP), it can self-assemble into highly-ordered microdomains with a wide range of morphologies and sizes that can be subsequently transferred into a functional material layer. This provides an effective pathway for fabrication of useful nanostructures in a rapid and low-cost process. BCPs thus offer a path to meso-scale patterning techniques and are promising candidates for enabling sub-10 nm nanolithography for the semiconductor industry. Poly(styrene-b-dimethylsiloxane) (PS-b-PDMS) is of particular interest due to its relatively large Flory-Huggins segmental interaction parameter ( χ~ 0.27 at room temperature), which leads to a high driving force for microphase separation. BCPs with high χ value demonstrate strong microphase separation, low defectivity, and sharp interfaces between different blocks, resulting in lower line edge roughness. Furthermore, the Si-containing PDMS block is etch-resistant compared to PS when subjected to an oxygen plasma, which is desirable for pattern transfer.
Although BCPs with small period have received much attention, the self-assembly of BCPs with large period (~100nm) is also important for photonic or phononic applications. High molecular weight PS-b-PDMS possesses large segregation strength (χN >>100, with N the degree of polymerization), but the kinetics of the microphase separation are limited due to high chain entanglement and low diffusivity. Here we describe the thin film morphology of a 123 kg/mol PS-b-PDMS BCP processed by solvent vapor annealing at room temperature. The kinetics of thin film morphology evolution was illustrated as a function of as-cast film thickness (50~90 nm), the composition of the binary mixture of solvent vapors (toluene:heptane) and the solvent annealing time (1~24 hr). Thin film structures with long-range (micron scale) ordered PDMS in-plane cylindrical domains with period of 90 nm were achieved after a 12 hr 5:1 toluene:heptane mixture vapor annealing. The conditions of as-cast thickness of 80 nm and swelling ratio of 2.68 enables the commensurability between the swelled film thickness and block copolymer period, leading to a uniform, monolayer cylinders formed over the film without severe terrace and hole formation. The directed self-assembly of the BCP within lithographically patterned trench confinement was demonstrated, showing alignment of the cylinders parallel to the sidewalls. Fabrication of ordered cobalt nanowire arrays by pattern transfer is also demonstrated, and their magnetic properties and domain wall behavior characterized. This study shows how the kinetic limitations inherent to large period BCPs can be overcome, enhancing their utility in energy applications such as photonic crystals and solar cells.
8:00 PM - BM7.3.30
Block Copolymers Nanostructures for Periodic Inorganic Oxides Synthesis
Krishna Pandey 1 , Calbi Gunder 1 , Mahua Biswas 1
1 Missouri State University Springfield United StatesShow Abstract
Tuning the shape and size of nanostructure materials with their unique properties is an area of great interest for the development of nanoscience and nanotechnology . Among several approaches to achieve this goal block copolymers (BCPs) have received considerable attention recently, due to the inherent self-assembly property which can lead to various nanoscopic structures, like spheres, cylinders, bicontinuous gyroids, and lamellae, depending on the composition and chain architecture of the BCPs . The well-aligned and periodic nanostructures of BCPs can be used as template of inorganic oxide patterning for microelectronics and optoelectronics applications. In this work we are using cylindrical polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) and spherical micelles structures polystyrene-block-poly(2-vinylpyridine) (PS-b-P2VP) BCPs as template for the inorganic oxides deposition. TiO2 with unique structural and functional properties can be extensively used in photo catalysis, water splitting, solar cells, supercapacitors and lithium-ion batteries . For TiO2 nanostructures synthesis we are using two methods. In the first method, we are using a unique solution process deposition method to deposit the oxide inside selective blocks of the copolymers. In the second method, we are using pulse laser deposition (PLD) method as the TiO2 deposition method after selectively etching one copolymer. After removing the polymers using calcination, the inorganic nanostructures can be used for various microelectronic, catalytic and optoelectronic applications.
S. Barth et. al., Progress in Materials Science , 55 (6), 563-627, (2010).
Y. Tseng et. al., Polymers, 2, 470-489, (2010).
M. Ge et. al., Journal of Materials Chemistry A, 4, 6772, (2016).
Guihua Yu, Univ of Texas-Austin
Haiqing Lin, SUNY Buffalo
Ho Bum Park, Hanyang University
BM7.4: Novel Structures I
Tuesday AM, November 29, 2016
Hynes, Level 2, Room 202
8:00 AM - *BM7.4.01
High Chi Block Copolymers and Photopatternable Interfaces for Controlling Thin-Film Structure
Christopher Ellison 1 , C. Grant Willson 1
1 University of Texas at Austin Austin United StatesShow Abstract
Patterning micro- and nano-scale features are broadly desired because of their high technological relevance to many applications, including microelectronics, magnetic storage media and a range of devices that impact energy. A general trend in this area is that device structures shrink in size with every new device generation and traditional lithography strategies (i.e., photoresists light exposed through photomasks within projection systems) are continually being challenged to reach targets. In recent years, complementary strategies are gaining more traction in academia and industry. One promising approach involves exploiting block copolymers (BCPs) that naturally self-assemble into domains ~1-100 nm in size. However, a major challenge is that their self-assembled structures must be directed into device relevant arrangements to be useful for manufacturing. I will provide an overview of our efforts in this area and then focus on a specific photochemical process for controlling BCP domain orientation in an area selected manner.
8:30 AM - BM7.4.02
Towards the Next Generation of Functional Nanomaterials—Metal-Organic Framework Templated PEDOT
Tiesheng Wang 1 2 , Stoyan Smoukov 1 , Anthony Cheetham 1 , John Madden 3 , Meisam Farajollahi 3 , Sebastian Henke 4 , Tongtong Zhu 1 , Shijing Sun 1
1 Department of Materials Science amp; Metallurgy, University of Cambridge Cambridge United Kingdom, 2 EPSRC Centre for Doctoral Training in Sensor Technologies and Applications, University of Cambridge Cambridge United Kingdom, 3 Advanced Materials and Process Engineering Laboratory, University of British Columbia Vancouver Canada, 4 Ruhr-Universität Bochum Lehrstuhl für Anorganische Chemie II Bochum GermanyShow Abstract
Porous conductive networks are highly desired for energy conversion and storage, catalysis and chemical sensing. PEDOT is a stable (thermally, chemically and electrochemically), biocompatible polymer with a wide range of applications, but it hasn’t been made into regular nanoporous materials. MOFs, on the other hand, have highly regular open framework structures, but are not conductive and generally fragile. Use of metal-organic frameworks (MOFs) as templates for PEDOT nanostructures promises to create novel conductive nanostructured materials, which are flexible, have high surface area, and novel reactivity. Here we present a wet-chemistry approach to achieving sub-millimeter sized materials of nanostructured poly(3,4-ethylenedioxythiophene) (nano-PEDOT) and conductive PEDOT-MOF composites. We perform extensive characterization of the materials both by spectrometry and by microscopy of the micrometer-structures from these materials.
Electrical property measurement via conductive AFM shows insulating behavior for the pure MOF and reveals semiconductor-like current-voltage curves for both the PEDOT-MOF composite and nano-PEDOT. The Young’s modulus obtained by nanoindentation for nano-PEDOT (ca. 0.5 GPa) is lower than the bulk PEDOT (ca. 2 GPa). Currently, open-channel nanostructures are mostly realized by methods such as inverse opals with pore normally larger than 50 nm. Here, we break that limit by using a MOF as the template, with pores/channels smaller than 2 nm in diameter. We believe the work will stimulate fundamental studies of polymer reactions in confinement and the discovery of other MOF-polymer systems where the MOF can act as a (sacrificial) template. Meanwhile, such pores/channels offer potential enhancements in species migration and chemisorption on a large area. These novel structures, combined with the stability and conductivity advantages of PEDOT, will be beneficial for numerous applications related to energy conversion and storage, such as supercapacitors and full cells.
8:45 AM - BM7.4.03
Ferroelectric Polymer Nanostructures on Flexible Substrates by Reverse Nanoimprint Lithography
Jingfeng Song 1 3 , Haidong Lu 1 3 , Keith Foreman 1 3 , Shumin Li 2 3 , Li Tan 2 3 , Shireen Adenwalla 1 3 , Alexei Gruverman 1 3 , Stephen Ducharme 1 3
1 Physics and Astronomy University of Nebraska-Lincoln Lincoln United States, 3 Nebraska Center for Materials and Nanoscience Lincoln United States, 2 Mechanical and Materials Engineering University of Nebraska-Lincoln Lincoln United StatesShow Abstract
Ferroelectric polymer nanostructures are of great interest due to their potential use in a wide range of applications. With the increasing application of ferroelectric polymer in the area of flexible electronics,1,2 high-throughput and low-cost fabrication of 2D and 3D ferroelectric polymer nanostructures on flexible substrates can be a significant basis for future research and applications. Here, we report that large arrays of ferroelectric polymer nanostripes and nanopillars can be fabricated directly on soft, flexible substrates by soft-mold reverse nanoimprint lithography (reverse NIL) at 135 °C and at pressures as low as 3 bar.3,4 The low pressure reverse NIL approach is compatible with flexible substrates with conductive thin film electrodes. More importantly, it leaves little or no residual polymer layer in-between the nanostructures, which obviates the need for additional etching processes that arise with conventional low-contrast nanoimprinting. The ferroelectric polymer nanostructures were highly uniform over large areas of at least 200 × 200 µm and had good crystallinity with nearly optimum (110) orientation. The ferroelectric properties of individual nanostripes or nanopillars were probed by piezoresponse force microscopy, which showed that they exhibited switchable and bi-stable polarization. In addition, the polarization hysteresis loops probed by pyroelectric measurements of the entire array showed that the nanostructure capacitor arrays had good ferroelectric switching characteristics, over areas of at least 1 mm × 1 mm.
Furthermore, our most recent results showed that ferroelectric nanostructures with remarkably smaller size beyond the designed nanoimprinting mold cavities could be prepared due to the unique nanoconfined self-assembly properties of the ferroelectric copolymer during the reverse NIL process. The reverse NIL method described here is a high-yield, low cost, scalable, and highly customizable method that provides a promising alternative to the traditional rigid-mold high pressure direct nanoimprinting processes. This method may facilitate future studies of functional polymer nanostructures for applications in flexible electronics, electro-mechanics, and energy harvesting.
 S. K. Hwang, I. Bae, R. H. Kim, and C. Park, Adv Mater 24 (44), 5910 (2012).
 L. Persano, C. Dagdeviren, Y. W. Su, Y. H. Zhang, S. Girardo, D. Pisignano, Y. G. Huang,
and J. A. Rogers, Nat Commun 4 (2013).
 J. Song, H. Lu, K. Foreman, S. Li, L. Tan, S. Adenwalla, A. Gruverman, and S. Ducharme,
J Mater Chem C (2016).(back cover)
 J. Song, H. Lu, S. Li, L. Tan, A. Gruverman, and S. Ducharme, Nanotechnology 27(1),015302 (2016).
9:00 AM - BM7.4.04
Dopant Induced Solubility Control Patterning of Conjugated Polymers
Ian Jacobs 1 , Jun Li 1 , Faustine Wang 1 , Adam Moule 1
1 University of California, Davis Davis United StatesShow Abstract
The solubility of semiconducting polymers can be “switched off” using addition of a high electron affinity molecular dopant. Spontaneous charge transfer with the dopant generates an organic salt that is completely insoluble in non-polar solutions. Here we demonstrate both chemical and optical mechanisms by which the doping can be reversed and the solubility of the polymer is “switched back on.” Using these techniques, we are able to vertically stack and laterally pattern mutually soluble polymer layers, which are vital processing steps needed to expand the use of organic semiconductors in device applications. Optimization of these techniques has yielded diffraction limited optical film patterning with regular features of 200-300 nm with only solution processing steps and direct write laser patterning. Comparison of patterned and initial samples shows no change in the optical, electrical or chemical properties of the polymer. This means that the film is quantitatively dedoped after the patterning process is complete yielding intrinsic semiconducting polymer that is nano-patterned. Dopant induced solubility control (DISC) patterning offers a new avenue to process semiconducting polymers with applications in all areas of organic electronics and in particular for PV and thermoelectric devices.
9:15 AM - BM7.4.05
Template Guided Fabrication and Transfer of Non Close Packed Colloidal Array on a Flat Substrate
Meneka Banik 1
1 Indian Institute of Technology Kharagpur Kharagpur IndiaShow Abstract
Ordered non close packed (NCP) array with colloidal particles are central to various applications such as optics, photonics, sensing, surface patterning etc. We report a simple, facile spincoating based approach for fabricating two dimensional colloidal crystals with hexagonal and non hexagonal close packed (HCP) arrays with organic as well as inorganic colloidal particles on flat and nano patterned substrates, respectively. Appropriate amounts of surfactant molecules are added to the colloidal dispersion ahead of spin coating to ensure the formation of the HCP patterns. The non-HCP arrays are fabricated by spin coating the particles onto soft lithographically. The substrate patterns impose directionality to the particles by confining them within substrate grooves during spin coating, thereby breaking the hexagonal close packed symmetry into structures that are commensurative with the substrate patterns. Parameters like coating speed, dilution of the colloids, amount of surfactant added and volume dispensed provide a control over the formation of HCP as well as the number of layers deposited.
We have also developed a novel technique by which the HCP as well as non-HCP array of the colloidal particles can be transferred to planar as well as non-planar surfaces. For this purpose the colloidal arrays are fabricated on a sacrificial PMMA layer which is subsequently degraded by UV exposure, resulting in transfer of the particles onto any other substrate, including non-planar, curves and rough surfaces. This allows the colloidal structures to be transported across substrates irrespective of their surface energy, wettability or morphology. Since the particle array is transferred onto a substrate, without exposing it to any kind of chemical or thermal environment, it can be utilized for placing particles on top of thin film solar cells for improving their absorption efficiency, without subjecting the completed cell to any further solution processing.
1. R. A. Weiss, X. Zhai, and A.V. Dobrynin, Langmuir 24, 5218-5225 (2008).
2. N. V. Dziomkina, and G. J. Vancso, Soft Matter 1, 265-272 (2005).
3. P. Jiang, T. Prasad, M. J. McFarland, and V. L. Colvin, Appl. Phys. Lett. 89, 011908-011916 (2006).
9:30 AM - BM7.4.06
Efficient Infrared Absorber with Mask-Free Anti-Reflecting Nanopillar Structure
Dezhao Li 1 , Baoling Huang 1
1 Hong Kong University of Science and Technology Hongkong Hong KongShow Abstract
Robust thermal radiation absorber with high absorbance is very attractive for detection applications. Quarter-wavelength coatings can realize high absorption but only for a particular wavelength. Metal-black coating can provide broad band absorption but it is very fragile. Anti-reflective nanostructures can reduce the reflection and improve the absorption of light from wide angles of incidence over a broad wavelength region. Based on the self-assembling of polyimide in oxygen plasma etching, an extremely low cost approach is developed to generate small controllable patterns for anti-reflective structure fabrication. By tuning dry etch recipes, inorganic nanopillar structures with heights of 200~ 700nm, diameters of 300~1000 nm and lateral spatial frequency in the range (1~10um-1), are fabricated. With the combination of suitable stack layers and thin metal layer coating, perfect broad-band infrared absorber (nearly 100% absorption in certain wavelength regions) has been developed through suppressing the reflection because of the light bend propagation in fabricated subwavelength structure. This strategy can be applied to different materials to form tunable multi-band absorber for targeted applications.
10:15 AM - *BM7.4.07
Stabilizing Proteins in Organic Solvent toward Functional Hybrid Materials
Ting Xu 1 2 3 , Brian Panganiban 1 4 , Christopher DelRe 1 , Baofu Qiao 5 , Mona Obadia 1 , Izaac Sit 1 , Monica Olvera de la Cruz 5 , Eric Drockenmuller 2 3
1 Department of Materials Science and Engineering University of California, Berkeley Berkeley United States, 2 Department of Chemistry University of California, Berkeley Berkeley United States, 3 Materials Science Division Lawrence Berkeley National Laboratory Berkeley United States, 4 Laboratoire d’Ingénierie des Matériaux Polymères Université Claude Bernard Lyon 1 Villeurbanne Cedex France, 5 Department of Materials Science and Engineering Northwestern University Evanston United StatesShow Abstract
Protein-based materials have the potential to change the current paradigm of material science. However, it still remains a challenge to preserve protein structure and functionality while making them readily processable. Our recent studies show that through the development of rationally designed statistically random copolymers, it is possible to stabilize proteins and process them in organic solvents, a common condition for material fabrication. Using horseradish peroxidase as model system, we have successfully tailored a polymer-based protecting agent that stabilizes enzymes at multiple hierarchical levels and has allowed for the retention of its activity when processed in organic solvents. Furthermore, the modularity of this approach has been confirmed through incorporation of other proteins that differ in size, surface chemistry, and functionality.
10:45 AM - BM7.4.08
Dewetting and Rupture Mechanism of Liquid Crystal Thin Film on Topographically Patterned Substrates
Palash Dhara 1 , Rabibrata Mukherjee 1
1 Indian Institute of Technology Kharagpur Kharagpur IndiaShow Abstract
Dewetting is a phenomenon where thin film tends to rupture due to destabilizing attractive Van-der Waal’s interaction and formed isolated random droplets . Dewetting study become very fascinating problem to encounter not only for understanding the fundamental physics but for fabrication of nanoscale or mesoscale non lithographic structure of soft materials like homo-polymer, block co-polymer,liquid crystal (LC) etc. Here, we have reported the dewetting and rupture mechanism of liquid crystal (5CB) thin film on patterned substrates (one dimension grating and two dimensions cross pattern) and then tried to co-relate the rupture mechanism with initial film thickness and surface structural effect. It is seen in experiments that rupturing of liquid crystal thin films on topographically patterned substrates is independent of surface heterogeneity which shows different mechanism than homo-polymer dewetting on patterned substrates. Pattern directed dewetting has been observed for homo-polymer like polystyrene on patterned substrates . We have also reported the morphology, macroscopic orientation and phase transition of spin dewetted LC (5CB) meso scale droplets on flat and topographically patterned substrates. Spin dewetting is very unique process where dewetting and rupturing of an ultra thin film occurs during the spin coating process itself with very low concentration of casting material and formed isolated random droplets . This spin dewetted random LC droplets were aligned by coating on different periodic structural surfaces. Complete dewetting and rupturing process of LC thin films as well as morphology and phase transition of spin dewetted LC droplets have been observed under optical polarised microscope and atomic force microscope platform.
. Reiter, G., Phys. Rev. Lett., 1992, 68, 75.
. Roy, S., Mukherjee, R., ACS Appl.Mater. Interfaces., 2012, 4, 5375.
. Bhandaru, N., Das, A., Salunke, N., Mukherjee, R., Nano Lett., 2014, 14(12), 7009.
11:00 AM - BM7.4.09
Ordering and Miniaturization in Dewetting of Pre-Patterned Thin Polymer Films on Flat Substrates
Nandini Bhandaru 1 , Rabibrata Mukherjee 1
1 Indian Institute of Technology Kharagpur Kharagpur IndiaShow Abstract
Ultrathin unstable polymer films exposed to a solvent vapor dewet by the growth of surface instability, the wavelength of which depends on the film thickness. We show that meso patterns present on the surface of a polymer thin film can engender an ordered dewetted morphology under certain specific conditions. The pre-patterned polymer thin film undergoes pattern directed rupture along the thinnest parts of the film when the initial local thickness over these zones (hrm) is reduced to a limiting thickness (hlim » 10 nm). In addition, depending on the periodicity of the imprinted patterns, the wavelength of instability corresponding to hrm must be lower than the width of the patterned grooves (ls). A morphology phase diagram is constructed which indicates a transition from the surface tension induced flattening to the ordered pattern directed rupture. The versatility of this technique is shown in its ability to form myriad of aligned meso-patterns starting from a simple grating structure on the film surface. The morphology of the evolving patterns is controlled by several parameters including the initial film thickness (hF), pre-pattern amplitude (hst), duration of solvent vapor exposure and wettability of the stamp used for pre-patterning the film. The evolution can be interrupted at any intermediate stage by removal of solvent vapor thereby achieving patterns on demand, which are well ordered as well as significantly miniaturized as compared to features obtained from dewetting of a flat film of same initial thickness. This concept is further be extended in multi polymer systems for obtaining ordered structures by dewetting of a thin polymer bilayer with a topographically structured interface.
11:15 AM - BM7.4.10
Highly-Ordered Cylindrical, Lamellar and Gyroid Domains Produced from Si-Containing Block Copolymer Thin Films
Karim Aissou 1 , Muhammad Mumtaz 1 , Segolene Antoine 1 , Guillaume Fleury 1 , Eric Cloutet 1 , Cyril Brochon 1 , Georges Hadziioannou 1
1 Laboratoire de Chimie des Polymeres Organiques Pessac Cedex FranceShow Abstract
The self-assembly of solvent-annealed block copolymer thin films susceptible to microphase separate into cylindrical, lamellar and gyroid phases is investigated. Here, we report on untemplated and templated semicrystalline poly(1,1-dimethyl silacyclobutane)-block-polystyrene (PDMSB-b-PS) thin films enabling the production of highly-ordered patterns with sub-10 nm features. These periodic structures, consisting of easily etchable PDMSB cylinders or lamellae with an out out-of-plane orientation separated by PS domains, are suitable for next generation lithography. We also explore the directed self-assembly of sub-100 nm thick PDMSB-b-PS layers into a double gyroid structure with long-range 211 plane ordering achieved by using topographical substrates. Such a morphology consisting of two continuous interpenetrating networks in 3D space makes them a good candidate to fabricate efficient device active layers.
11:30 AM - BM7.4.11
Organic Passivation of Silicon Through Multifunctional Polymeric Interfaces
Mariela Castillo 2 , Asli Ugur 2 , Hossein Sojoudi 2 , Nathan Nakamura 1 , Zhe Liu 3 , Fen Lin 3 , Riley Brandt 2 , Tonio Buonassisi 2 , B. Reeja Jayan 1 , Karen Gleason 2
2 Massachusetts Institute of Technology Cambridge United States, 1 Carnegie Mellon University Pittsburgh United States, 3 National University of Singapore Singapore SingaporeShow Abstract
We demonstrate a solvent-free, low temperature (25-170 °C) approach using chemical vapor deposition (CVD) grafting and polymerization processes to passivate the unpaired electrons or “dangling” bonds on the surface of silicon. These bonds behave as charge carrier recombination centers, thereby lowering the overall operating efficiency of silicon devices for applications like photovoltaics. The multifunctional (dielectric and electronically conducting) passivating layers described in this work achieves several orders of magnitude improvement in minority carrier lifetime (> 2 milliseconds) compared to bare silicon (~ 30 microsecond), and remained stable in air for over 200 hrs. These values approach that of silicon nitride (SiNx) films deposited at significantly higher temperatures (> 400 oC).
Two CVD polymerization processes were carried out in sequence, namely initiated (iCVD) and oxidative (oCVD). iCVD covalently grafts the polymer film directly onto the silicon substrate by initiating a chemical reaction between the surface hydride bonds on silicon and the reactive vinyl (C=C) groups on the monomer; thereby satisfying surface dangling bonds and “passivating” electrically active interface states. We explored three iCVD monomers of varying sizes, which polymerize to form dielectric passivation layers. To obtain the conducting passivation layer, oCVD was used to graft poly(3,4-ethylenedioxythiophene) (PEDOT) films to the unreacted vinyl groups of the iCVD grown polymer layer.
The polymer passivation processes can reduce surface recombination rates through a combination of (1) reduction of the surface state density (iCVD) and (2) adjustment of the charge (electron or hole) carrier concentrations at the silicon surface by altering interfacial band bending (oCVD). We demonstrate this results using a combination of quasi-steady state and transient photoconductance measurements; effective charge and band bending calculations; and surface characterization using x-ray photoelectron spectroscopy (XPS). Passivation quality also improved on grafting aliphatic monomers compared to aromatic ones suggesting a reduction in steric effects in the former, helping us posit design rules for polymer based surface passivation of silicon. Additionally, tests using a nanomechanical tester reveal that grafting eliminates cracking and delamination via the strong covalent chemical bonds formed at the substrate-film interface.
The mild CVD processes retain delicate organic functionalities in the monomers, enabling the subsequent growth of both insulating/dielectric and conducting polymer layers on top, potentially serving diverse functionalities. Examples in solar cells include dielectric antireflective coatings and patterned conducting polymer grids to replace the expensive silver metallization. Finally, the ability to use an electrically conducting polymer for passivation creates a direct interface between traditional silicon microelectronics and organic electronics.
11:45 AM - BM7.4.12
Laser Induced Hierarchically Porous Structures from Block Copolymer–Directed Self-Assembly
Kwan Tan 2 1 , Michael Thompson 2 , Ulrich Wiesner 2
2 Materials Science and Engineering Cornell University Ithaca United States, 1 Low Energy Electronic Systems IRG Singapore-MIT Alliance for Research and Technology Singapore SingaporeShow Abstract
Hierarchical porous structured materials are highly desirable for a large plethora of applications, ranging from separation, sensing, energy conversion and storage, to tissue engineering. However synthesis of hierarchical materials with multi-dimensional complexities and novel functional properties remains challenging. Here we describe the controlled generation of hierarchically porous polymer structures and shapes coupling block copolymer-directed self-assembly with spatially localized transient laser irradiation. The combined approach further provides pathways to electrically conducting carbon structures, as well as generation of complex crystalline silicon nanostructures. The method is compatible with standard semiconductor manufacturing processes and suitable to fabricate porous structures with high surface area and connectivity for integrated energy storage and sensing applications.
BM7.5: Novel Structures II
Tuesday PM, November 29, 2016