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
9:00 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.
9:30 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.
9:45 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.
10:00 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.
10:15 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.
11:00 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.
11:30 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.
11:45 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).
12:00 PM - 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 %).
12:15 PM - 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.
12:30 PM - 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
2:30 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.
3:00 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.
3:30 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.
3:45 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.
4:00 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.
4:30 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.
5:00 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.
 S. Choi, J. H. Drese and C. W. Jones, ChemSusChem, 2009, 2, 796–854.
 S. Lee and S. Park, J. Ind. Eng. Chem., 2015, 23, 1–11
 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.
5:15 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 .
5:30 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
9:00 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.
9:00 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.
9:00 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.
9:00 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.
9:00 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.
9:00 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.
9:00 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 t