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Examining Structure Property Relationships Of Proton Exchange Membranes Through The Study Of Model Sulfonated Graft Copolymers
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Book Synopsis Examining Structure-Property Relationships of Proton Exchange Membranes Through the Study of Model Sulfonated Graft Copolymers by : Ching-Ching Ami Yang
Download or read book Examining Structure-Property Relationships of Proton Exchange Membranes Through the Study of Model Sulfonated Graft Copolymers written by Ching-Ching Ami Yang and published by . This book was released on 2014 with total page 187 pages. Available in PDF, EPUB and Kindle. Book excerpt: The role of polymer nanostructure on morphology, crystallinity, water sorption and proton conductivity was investigated using a model solid polymer electrolyte. Poly([vinylidene difluoride-co-chlorotrifluoroethylene]-graft-styrene) [P(VDF-co-CTFE)-g-PS], which consists of a hydrophobic, fluorous backbone and styrenic graft chains of varied length was synthesized with controlled chain architecture and chemical composition. The polystyrene graft chains were sulfonated to different degrees to provide three series of polymers with controlled ion exchange capacity (IEC). Due to chemical dissimilarity of the hydrophobic fluorous segments and the hydrophilic sulfonated polystyrene segments, the copolymers phase separate into ionic and non-ionic domains. The ionic domains allow transport of water and protons; the hydrophobic domains provide mechanical integrity, preventing the membranes from dissolving in water. The design of the model graft copolymers allows systematic examination of the effects of graft length and graft density on water sorption and proton conductivity. One of the major features of this work is that the sulfonated graft copolymers with shortest graft chains exhibit highest degree of crystallinity and highest PVDF content, which restrict excessive swelling and alleviate acid dilution, leading to a wider IEC operating range for high proton conductivity. Furthermore, the short graft copolymers allow access to very high IEC membranes that are insoluble in water. These short graft polymers with high IECs exhibit exceptionally high proton conduction under reduced humidity and elevated temperatures. In addition, for a given PVDF content, the lower graft density copolymers were observed to possess higher crystallinity and more contiguous PVDF domains that allow high IEC membranes to be prepared that possess lower degrees of swelling. Another important finding is that blending fully sulfonated graft copolymers with high molecular weight PVDF yields membranes with overall low IECs that exhibit highly localized ion content. This promotes the interconnection of ionic domains for effective proton transport while the more extended hydrophobic domains significantly reduce excessive swelling which serve to maintain the mechanical property of the membranes. This thesis describes a systematic approach, demonstrating the design, synthesis, characterization of model polymers, followed by the analysis of structure-property relationships in proton exchange membranes.
Book Synopsis An Investigation of Structure-property Relationships in Several Categories of Proton Exchange Membranes by : Marianne Phelan Rodgers
Download or read book An Investigation of Structure-property Relationships in Several Categories of Proton Exchange Membranes written by Marianne Phelan Rodgers and published by . This book was released on 2007 with total page 394 pages. Available in PDF, EPUB and Kindle. Book excerpt: The chemical and structural features of proton exchange membranes (PEMs) are related to their fuel cell relevant properties. The objective of this work is to understand structure-property relationships in PEMs through the fabrication and characterization of several classes of membranes. Incorporation of linear and angled monomers into the main chain of a polyimide permitted investigation of the effect of kinked versus linear polymers on membrane properties. The conductivity of angled sulfonated polyimide membranes is greater than those prepared from linear polymers, but water uptakes are lower. These differences are attributed to increased entanglements of angled polymers, which limit the degree of swelling and lead to increased proton concentration. Polyelectrolytes were incorporated into reinforcing materials to study the effect of incorporating and confining polyelectrolytes in the pores of reinforcing materials. The employment of reinforcing materials reduces conductivity, mobility, and permeance due to decreased ionomer content and connectivity of the ionomer. However, membranes are stronger and thinner, which compensates for these losses in terms of lower resistance and increased dimensional stability. Incorporating zirconium hydrogen phosphate (ZrP) and silicon dioxide (SiO2) into Nafion℗ membranes permitted investigation of their effect on membrane properties. Data for Nafion℗/ZrP membranes support the theory that ZrP disrupts cohesive forces in Nafion℗, causing it to absorb more water. The increased water content of the membranes does not result in increased conductivity because there is a concurrent decrease in proton concentration and mobility due to poorly conducting ZrP disrupting the conduction pathway and increased water content diluting protons and separating proton conduction sites. The decreasing density of the Nafion℗/SiO2 composite membranes with increasing SiO2 content and the increased dimensional stability of the membranes increasing compared to unmodified Nafion℗ support the theory that a rigid scaffolding forms. Due to formation of void space that increases with increasing SiO2 content, water content increases, thus diluting the protons in the membrane, leading to lower conductivity. These structure-property relationships may be relevant to other membrane systems and should be considered when designing alternative systems for proton exchange membranes.
Book Synopsis Water Hydrogen Bonding in Proton Exchange and Neutral Polymer Membranes by : Sarah Smedley
Download or read book Water Hydrogen Bonding in Proton Exchange and Neutral Polymer Membranes written by Sarah Smedley and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Understanding the dynamics of water sorbed into polymer films is critical to reveal structure-property relationships in membranes for energy and water treatment applications, where membranes must interact with water to facilitate or inhibit the transport of ions. The chemical structure of the polymer has drastic effects on the transport properties of the membrane due to the morphological structure of the polymer and how water is interacting with the functional groups on the polymer backbone. Therefore studying the dynamics of water adsorbed into a membrane will give insight into how water-polymer interactions influence transport properties of the film. With a better understanding of how to design materials to have specific properties, we can accelerate development of smarter materials for both energy and water treatment applications to increase efficiency and create high-flux materials and processes. The goal of this dissertation is to investigate the water-polymer interactions in proton exchange and uncharged membranes and make correlations to their charge densities and transport properties. A linear Fourier Transform Infrared (FTIR) spectroscopic method for measuring the hydrogen bonding distribution of water sorbed in proton exchange membranes is described in this thesis. The information on the distribution of the microenvironments of water in an ionic polymer is critical to understanding the effects of different acidic groups on the proton conductivity of proton exchange membranes at low relative humidity. The OD stretch of dilute HOD in H2O is a single, well-defined vibrational band. When HOD in dilute H2O is sorbed into a proton exchange membrane, the OD stretch peak shifts based on the microenvironment that water encounters within the nanophase separated structure of the material. This peak shift is a signature of different hydrogen bonding populations within the membrane, which can be deconvoluted rigorously for dilute HOD in H2O compared to only qualitative observations that can be made with pure D2O or H2O. The theory and experimental practice of determining the hydrogen bonding distribution of water in a range of proton exchange membranes bearing aromatic sulfonate and perfluorosulfonate groups using this OD stretch technique is discussed. The OD stretch of dilute HOD in H2O absorbed in a series of sulfonated syndiotactic poly(styrene) and sulfonated poly(sulfone) membranes was studied using FTIR spectroscopy to measure how the character of the sulfonate headgroup and the backbone polarity influenced the water-membrane interactions. Using a three-state model, the OD stretch yielded information about the populations of absorbed water participating in hydrogen bonds with polymer-tethered sulfonate groups, water in an intermediate state, or water hydrogen bonding with other water molecules. The perflouroalkyl sulfonate moiety, which behaves as a superacid, consistently displayed the largest fraction of headgroup-associated water due to its strong acidic character. Measurements of the OD stretch gave insight to the strength of the hydrogen bonds formed between water and the sulfonate groups. Water associated with the superacid displayed an OD stretch peak position that was blueshifted by 39 cm-1 compared to the aryl sulfonate associated water with an OD stretching frequency that was centered at 2547 cm-1. The polarity of the polymer backbone also affected the OD stretch peak position. As hydration increased, the OD peak stretching frequency in poly(styrene)-based membranes displayed a redshift from 2566 cm-1 to 2553 cm-1, whereas there was no OD peak maxima shift in poly(sulfone)-based membranes due to the greater amount of intermediate water in the more polar poly(sulfone) backbone system.To further understand how the acidity of the sulfonate can be altered and how the acidity affects the hydrogen bonding network of water in a polymer membrane, various polymers with small chemical differences in the perfluorosulfonate sidechain were studied. In addition to the vibrational spectroscopy measurements using HOD as a probe, the partial charges of the sulfonate groups were calculating using DMol3 DFT calculations. The calculations and the experimentally determined peak position of the OD stretch both correlated to give a ranking of acidity for the various sidechains. It was found that having a thioether linkage instead of an ether linkage (typical linkage for perflurosulfonates) increased the acidity of the sulfonate group due to the capability of sulfur to expand its octet and more readily accept additional electron density. Through DFT geometry optimization, it was discovered that the thioether linkage prefers a kinked configuration while the ether linkage gives a more linear sidechain structure. This structural configuration correlated to experimental findings allowing more water to interact with the sulfonate group containing the ether linkage than the thioether linkage due to the sulfonate group being more easily accessible, even though the thioether sidechain is more acidic.Three sulfonated poly(arylene sulfone) based polymers were studied using FTIR and DFT calculations to better understand how the acidity of the sulfonate groups were affected by the placement on the backbone. By increasing the number of sulfone groups, which have electron withdrawing properties, flanking the sulfonated aromatic ring, the acidity was increased. The charge density of a sulfonate group flanked by two sulfone groups was -1.626 (in units of fundamental charge), while the charge density of a sulfonate group flanked by one sulfone group increased to -1.703. Additionally, if the subsequent ring was unsulfonated, the charge density further increased to 1.737, indicating that some stability is gained by both available rings being sulfonated. The differences in charge density are reflected in the water uptake and conductivity measurements, where the samples with the lowest charge density had the highest water uptake and conductivity. The deconvoluted OD peak revealed that the sample with two sulfone groups flanking the sulfonated aromatic ring contains the highest amount of bulk-like water, which led to the increased conductivity. The polyamide active layer of commercially available reverse osmosis membranes was studied at various relative humilities to better understand how the structure of the active layer changes when hydrated. The fingerprint region was used to analyze changes in the vibrational signature of specific functional groups and to understand how different chemical moieties interact with water. Using the difference spectrum, the water-polymer interactions could be quantified and correlated to transport properties of the membrane. Increasing the amount of free carboxylic acid groups on the backbone will lead to an active layer that is less crosslinked and contains a greater number of larger pores, which results in a higher flux. Active layers that contained a smaller concentration of free carboxylic acids were more highly crosslinked and had a higher amount of smaller pores, resulting in a lower flux. In summary, by studying the water hydrogen bonding network in various proton exchange membranes and neutral polyamide membranes, a new understanding of structure-property relationships has been developed. This will lead to a greater understanding of transport properties and conductivity in various polymer membranes. Expanding this fundamental knowledge will lead to the development of smarter materials for energy and reverse osmosis applications, and the ideas developed here can be extended to new types of materials used for various needs.
Book Synopsis Structure-property-processing Relations in Sulfonated Block Copolymer Membranes by : Phuc Vinh Truong
Download or read book Structure-property-processing Relations in Sulfonated Block Copolymer Membranes written by Phuc Vinh Truong and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Ionic block copolymers combine the functionality of ionomers with the mechanical properties of thermoplastics, and are widely studied for applications in water purification and electrochemical devices. Membranes (thin films) are often prepared by solution casting. As the solvent evaporates, the strong incompatibility between ionic and non-ionic segments will trap non-equilibrium structures in the film. Consequently, the equilibrium block copolymer phase diagrams are poor predictors of membrane morphology, making it difficult to engineer the optimal domain sizes and transport pathways. The objective of this dissertation is to establish structure-property- processing relations of sulfonated pentablock copolymer (SPC) membranes. Films were prepared by casting from solvents of varying polarity, as the choice of solvent controls the solution state structure, and were characterized with complementary measurements that include X-ray scattering, microscopy, infrared spectroscopy, water uptake, impedance spectroscopy and tensile tests. First, we investigate the structure and transport properties of lamellar SPC membranes. All films were cast from mixtures of toluene and n-propanol. As the polarity of the casting solvent increases, the bulk structure becomes more disordered with a higher defect density, and the surface becomes more hydrophilic. These structural changes lead to enhancements in water uptake and proton conductivity. The onset of structural disorder coincides with a change in solvent selectivity towards the sulfonated domains. Therefore, the sulfonated block becomes more swollen during processing, which may induce defects that connect the neighboring sulfonated domains and produce a continuous structure. Next, we investigate the effects of hydration cycles on the structure and performance of commercial SPC films, which is relevant when evaluating their potential as water purification membranes or proton-conducting layers. We find that hydration cycling drives a structural transition from isolated micelles with a sulfonated core to a network of percolating sulfonated domains, which is beneficial for transport. However, hydration cycling can also induce mechanical instabilities that reduce swelling, water uptake and ductility. Consequently, transport properties are governed by the tradeoff between nanoscale restructuring and macroscale buckling. Significantly, we believe that our methodology and findings will be useful for design, optimization, and fundamental investigations of other ionic block or random polymer systems.
Book Synopsis Synthesis and Characterization of Proton Conducting, Fluorine-Containing Block Copolymers by : Zhi Qing Shi
Download or read book Synthesis and Characterization of Proton Conducting, Fluorine-Containing Block Copolymers written by Zhi Qing Shi and published by . This book was released on 2004 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fuel cells are being investigated as environmental-friendly, highly efficient alternative power sources. Proton conducting membranes play a central role in proton exchange membrane fuel cells (PEMFCs), serving as both electrolyte and fuel separator. This thesis addresses the design, sythesis and characterization of novel flourine-countaining block copolymers, and the preparation and investigation of sulfonated block copolymers as model proton exchange membranes (PEMs). Poly([vinylidene diflouride-co-hexaflouropropylene]-b-styrene), P[VDF-co-HFP]-b-PS, block copolymers have been prepared by a combination of chain transfer radical polymerization and atom transfer radical polymerization. The strategy of producing trichloromethyl-terminated vinylic polymers by chain transfer polymerization has proven useful for the synthesis of macroinitiators for subsequent preparation of novel flourin-containing block copolymers. Another class of block co-polymer, based on bisphenol A polysulfone and poly(vinylidene flouride), (PSF-b-PVDF), has also been prepared by polycondensation of, -dihydroxy bisphenol A polysulfone precursors and, -dibromo polyvinylidene flouride. Both families of block copolymers, (P[VDF-co-HFP]-b-PS) and (PSF-b-PVDF), were subsequently sulfonated and acidified to yield several series of model proton exchange membranes that were used to examine the effect of flourous blocks on membrane morphology and proton conductivity. One of the key findings of this work is that athe conductivity of block copolymer membranes is significantly higher than that of random copolymer membranes indicating that block structures facilitate proton conductivity. Additionally, the conductivity of partially sulfonated P[VDF-co-HFP]-b-PS block copolymer membranes is higher than that of non-flourous block copolymer membranes. The flouropolymer block segments induce formation of connected ion channels which results in enhanced proton transport.
Book Synopsis Cellulose-Based Graft Copolymers by : Vijay Kumar Thakur
Download or read book Cellulose-Based Graft Copolymers written by Vijay Kumar Thakur and published by CRC Press. This book was released on 2015-04-23 with total page 622 pages. Available in PDF, EPUB and Kindle. Book excerpt: Cellulose-Based Graft Copolymers: Structure and Chemistry discusses the synthesis, characterization, and properties of multifunctional cellulose-based graft copolymers. Presenting the contributions of accomplished experts in the field of natural cellulosic polymers, this authoritative text: Offers an overview of cutting-edge technical accomplishmen
Book Synopsis Polymer and Small Molecule Designs for Anion Conducting Membranes by : Sedef P. Ertem
Download or read book Polymer and Small Molecule Designs for Anion Conducting Membranes written by Sedef P. Ertem and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Fuel cells are one of the oldest sustainable energy generation devices, converting chemical energy into electrical energy via reverse-electrolysis reactions. With the rapid development of polymer science, solid polymer electrolyte (SPE) membranes replaced the conventional liquid ion transport media, rendering low-temperature fuel cells more accessible for applications in portable electronics and transportation. However, SPE fuel cells are still far from commercialization due to high operation cost, and insufficient lifetime and performance limitations. Anion exchange membrane fuel cells (AEMFCs) are inexpensive alternatives to current proton exchange membrane fuel cell (PEMFC) technology, which relies on utilizing expensive noble-metal catalysts and perfluorinated SPE materials. Unlike PEMFCs, there is not an ideal AEM material that provides efficient ion transport, while being mechanically robust and chemically stable under strong alkaline conditions. The objectives of this dissertation are to investigate macromolecular design parameters to obtain robust membranes with efficient ion conductivities, and molecular design parameters to obtain alkaline stable ammonium cations as an alternative to the benchmark benzyltrimethylammonium (BTMA) cation. Macromolecular design parameters were explored by systematic variations of polymer architecture from random, to graft, to symmetric pentablock copolymer structures. Solvent processable random copolymers of polyisoprene-ran-poly(vinyl- benzyltrimethylammonium chloride) were synthesized via polymerization of commercially available monomers. Robust membranes were obtained by thermal or photocross-linking of unsaturated isoprene units. Depending on the copolymer composition, choice of cross-linking method, and the hydrophobicity of the cross-linker, microphase-separated morphologies were obtained forming a connected network of ion clusters. Connectivity improved ion conductivity by two to three orders of magnitude even at low hydration numbers. Connected ionic networks with larger domain sizes were obtained when polymer chains with fixed cations were grafted onto a hydrophobic backbone. Systematic change of graft length and graft density showed a strong correlation with domain connectivity. At a fixed graft density, increasing graft length improved domain connectivity and ion conductivity at the expense of excessive water uptake and dimensional instability. At a fixed graft length, increased graft density improved domain connectivity due to decreased domain size and distance, without compromising membrane dimensional stability. Compared to analogous random copolymers two to three times higher ion conductivities were obtained at relatively low hydration, reaching chloride ion conductivities as high as 50 mS/cm at 60 oC and 95 % relative humidity. A symmetric ABCBA pentablock was functionalized to obtain a midblock quaternary ammonium functionalized polymer that are analogous to midblock sulfonated Nexar® pentablock copolymers which have been commercialized by Kraton Polymers. X-ray scattering and transmission electron microscopy revealed formation of a microphase-separated inverse morphology where the minor ionic component formed the connected phase. Membranes had elastomeric properties and superior water management to graft copolymers while providing two to three times higher ion conductivity at an equivalent ion concentration. This work represents the first example of a midblock quaternized pentablock copolymer and the investigation of the structure-morphology-property relationships. Lastly, improved alkaline stability of hexyltrimethylammonium (HTMA) cations were investigated on a molecular level, by systematic structural design. Phenyl, phenyl ether, and benzyl ether attached HTMA small molecule cations were synthesized. These three spacer-modified cations were found to be six to ten times more stable than the conventional BTMA cation. The linker chemistry did not influence the overall alkaline stability, enabling easy access to stable ammonium cations. Analogous styrenic monomers, and their homopolymers were synthesized. High stability of the homopolymer cations was confirmed in comparison to poly(BTMA). This study provided a deeper understanding of ammonium degradation mechanisms under strong alkaline conditions, and proposed monomer designs for easy incorporation of stable ammonium cations onto polymers.
Book Synopsis Water and Salt Transport Structure/property Relationships in Polymer Membranes for Desalination and Power Generation Applications by : Geoffrey Matthew Geise
Download or read book Water and Salt Transport Structure/property Relationships in Polymer Membranes for Desalination and Power Generation Applications written by Geoffrey Matthew Geise and published by . This book was released on 2012 with total page 768 pages. Available in PDF, EPUB and Kindle. Book excerpt: Providing sustainable supplies of water and energy is a critical global challenge. Polymer membranes dominate desalination and could be crucial to power generation applications, which include reverse osmosis (RO), nanofiltration (NF), forward osmosis (FO), pressure-retarded osmosis (PRO), electrodialysis (ED), membrane capacitive deionization (CDI), and reverse electrodialysis (RED). Improved membranes with tailored water and salt transport properties are required to extend and optimize these technologies. Water and salt transport structure/property relationships provide the fundamental framework for optimizing polymer materials for membrane applications. The water and salt transport and free volume properties of a series of sulfonated styrenic pentablock copolymers were characterized. The polymers' water uptake and water permeability increase with degree of sulfonation, and the block molecular weights could be used to tune water uptake, permeability, and selectivity properties. The presence of fixed charge groups, i.e., sulfonate groups, on the polymer backbone influence the material's salt transport properties. Specifically, the salt permeability increases strongly with increasing salt concentration, and this increase is a result of increases in both salt sorption and diffusivity with salt concentration. The data for the sulfonated polymers, including a sulfonated polysulfone random copolymer, are compared to those for an uncharged polymer to determine the influence of polymer charge on salt transport properties. The sulfonated styrenic pentablock copolymer permeability data are compared to literature data using the water permeability and water/salt selectivity tradeoff relationship. Fundamental transport property comparisons can be made using this relationship. The effect of osmotic de-swelling on the polymers and the transport properties of composite membranes made from sulfonated styrenic pentablock copolymers are also discussed. The sulfonated styrenic pentablock copolymers were exposed to multi-valent ions to determine their effect on the polymer's salt transport properties. Magnesium chloride permeability depends less on upstream salt concentration than sodium chloride permeability, presumably due to stronger association between the sulfonate groups and magnesium compared to sodium ions. Triethylaluminum was used to neutralize the polymer's sulfonic acid functionality and presumably cross-link the polymer. The mechanical, transport, and free volume properties of these aluminum neutralized polymers were studied.
Book Synopsis Structure Property Relationships for Polymers Bearing Reversibly Associating Side-groups by : Christopher Lloyd Lewis
Download or read book Structure Property Relationships for Polymers Bearing Reversibly Associating Side-groups written by Christopher Lloyd Lewis and published by . This book was released on 2014 with total page 237 pages. Available in PDF, EPUB and Kindle. Book excerpt: "The objective of this research is to establish structure-property relationships for macromolecules bearing reversibly associating side-groups. In previous studies we demonstrated shape-memory behavior for elastomer networks bearing strong ureido-pyrimidinone (UPy) hydrogen-bonding side-groups. However, relationships between the underlying viscoelastic behavior and side-group features such as hydrogen bond strength, structure, the presence of a permanent network and distance of the binding group from the macromolecular chain are not well established. Further, while numerous studies focus on the associative behavior of polymers in solution, few have examined their bulk behavior. To address this need, copolymers bearing weak ([Delta]H ~ 30kJ/mol) or strong hydrogen ([Delta]H ~ 70kJ/mol) bonding side-groups (HBSGs) were copolymerized with a low glass transition (Tg) polymer backbone into linear and network polymers. For polymers bearing weak HBSGs the temperature dependence of viscosity could be attributed to the elevation of Tg alone whereas the rheological behavior of strong HBSG polymers could be attributed to side-group association. To explain our results, a 'state-of-ease' model was developed that assumes continuous mechanical equilibrium between applied stress and the stresses arising from a permanent network and a second network that continuously reforms. The model is able to predict various rheological responses for UPy containing polymers such as dynamic mechanical and shape-memory behavior. The influence of micro-environment can also influence viscoelastic behavior. To assess the ability of a strong HBSG to dimerize within water swollen environments the swelling and dynamic mechanical behavior of a hydrophilic polymer bearing UPy side-groups was studied. The presence of UPy reduced the rate of short-time swelling whereas long-time swelling increased with UPy concentration and was attributed to UPy disrupting the native polymer structure. While the presence of UPy dramatically increased the viscosity, it does not form a percolated network at low UPy concentrations, suggesting that UPy's efficacy is reduced in the presence of water. In summary, by systematically studying several model polymers, this thesis exposes the degree to which reversibly binding side-groups can affect rheology, solid mechanics, and water sorption. The acquired knowledge can form a basis for materials design of future self-healing and shape-memory polymers, thermoplastic elastomers, and other field-responsive polymers"--Pages viii-ix.
Book Synopsis Synthetic Methods in Step-Growth Polymers by : Martin E. Rogers
Download or read book Synthetic Methods in Step-Growth Polymers written by Martin E. Rogers and published by John Wiley & Sons. This book was released on 2003-08-08 with total page 619 pages. Available in PDF, EPUB and Kindle. Book excerpt: Alles über die Stufenwachstums-Polymerisation - von Syntheseverfahren und Reinigungsmethoden bis zur Charakterisierung der Produkte - finden Sie in diesem Buch. - bietet einen Ausblick auf zukünftige Trends - mit historischen Informationen - erläutert die Klassifikation von Stufenwachstumspolymeren
Book Synopsis Synthetic Design of Polysulfone Membranes: Morphological Effect on Property and Performance in Flow Batteries by : Brandon Philippe Gindt
Download or read book Synthetic Design of Polysulfone Membranes: Morphological Effect on Property and Performance in Flow Batteries written by Brandon Philippe Gindt and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation outlines a novel path towards improved understanding and function of proton exchange membranes (PEMs) for redox flow batteries, a large-scale battery storage device. This research uses synthetic methods and nanotechnology through two different approaches to prepare tailored polymer membranes:1) Ion exchange membranes with enhanced chemical structures to promote membrane morphology on the nano-scale were prepared. Specifically, functional polysulfones (PSUs) were synthesized from different pre-sulfonated monomers. These PSUs have controlled placement and content of unique sulfonic acid moieties. PEMs were fabricated and characterized. The new PEMs showed desirable physical properties and performance in a vanadium redox flow battery (VRFB) cell.2) Nanoporous PSU membranes were fabricated via post-hydrolysis of polylactide (PLA) from PLA-PSU-PLA triblock copolymer membranes. The controlled morphology and pore size of the resulting nanoporous membranes were evaluated by different microscopy and scattering techniques to understand structure-property relationships. Further, the resulting nanopore surface was chemically modified with sulfonic acid moieties. Membranes were analyzed and evaluated as separators for a VRFB. The chemically modified nanoporous PEMs exhibited unique behavior with respect to their ion conductivity when exposed to solutions of increasing acid concentration. In addition, the hierarchical micro-nanoporous membranes developed further showed promising structure and properties.
Book Synopsis Structure-property Relationships in Polyolefin Blends and Copolymers by : Feng Zuo
Download or read book Structure-property Relationships in Polyolefin Blends and Copolymers written by Feng Zuo and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Structure-Property Relationships of Polymers in Membranes by : Aditi Damle-Bijani
Download or read book Structure-Property Relationships of Polymers in Membranes written by Aditi Damle-Bijani and published by LAP Lambert Academic Publishing. This book was released on 2011-03 with total page 240 pages. Available in PDF, EPUB and Kindle. Book excerpt: Asymmetric Cellulose acetate membranes were first developed and used for water desalination. Though the inventors designed membranes to be porous on surface which would separate salt from water by adsorption of pure water on the surface, the prevailing scientific community felt it was diffusion of pure water from the membrane which caused separation. Even after polyamide RO membranes became available which were derived by surface modification of polysulfone UF membranes that were well recognized for their porous nature, the solution-diffusion theories continued. We were compelled to take up this work to give additional evidence for existence of pores on the surface of all membranes those could separate solutes from solutions. We demonstrated that application of vacuum at outlet of membrane should improve the flux only if the membrane was not a continuous surface. Applying vacuum at outlet of the membrane is not same as applying that much additional pressure at the feed side. Polyamides that cannot form continuous structures were synthesized and demonstrated to produce porous desalination RO Membranes, with higher flux under vacuum.
Book Synopsis Multi-block Sulfonated Poly(phenylene) Copolymer Proton Exchange Membranes by :
Download or read book Multi-block Sulfonated Poly(phenylene) Copolymer Proton Exchange Membranes written by and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Improved multi-block sulfonated poly(phenylene) copolymer compositions, methods of making the same, and their use as proton exchange membranes (PEM) in hydrogen fuel cells, direct methanol fuel cells, in electrode casting solutions and electrodes. The multi-block architecture has defined, controllable hydrophobic and hydrophilic segments. These improved membranes have better ion transport (proton conductivity) and water swelling properties.
Book Synopsis Synthesis and Structure-property Relationships of Polymeric Membranes for Small Molecule Transport by : Haomiao Yuan
Download or read book Synthesis and Structure-property Relationships of Polymeric Membranes for Small Molecule Transport written by Haomiao Yuan and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: One key challenge for alkaline anion exchange membrane fuel cells is the lack of alkaline stable polycations. The synthesis of random, crosslinked and block copolymers based on the cobaltocenium phenylene norbornene (NPC) monomer is described. The polymers were synthesized from ring-opening metathesis polymerization (ROMP) of the NPC monomer showed excellent thermo-alkaline and thermo-oxidative stability. Random copolymers, crosslinked networks and amphiphilic diblock copolymers were prepared by copolymerizing NPC with different hydrophobic monomers: norbornene for random copolymers, dicyclopentadiene for crosslinked networks and a norbornene dibenzyl ether monomer for amphiphilic diblock copolymers. Mechanical robust membranes were prepared from all these copolymers. Polymers with different architectures exhibited different morphologies. Random copolymers showed disordered interconnected cobaltocenium domains with ion clusters present; crosslinked networks showed homogenous distribution of ions; the amphiphilic diblock copolymers showed cylindrical microphase separation with the cationic domains being the continuous phase even though they constituted the minor volume component. The morphologies of the membranes were found to have little effect on the water uptake of the membranes, but significantly influenced the ionic conductivity. The crosslinked membranes showed lower conductivity compared to the random copolymer membranes at the same composition. However, higher IECs can be achieved by crosslinking with concomitant improved mechanical integrity relative to their random copolymer analogs, ultimately allows for reaching higher ion conductivity values. For the diblock copolymer, formation of a conducting ion channel and elimination of the presence of ion clusters allowed for significantly higher ionic conductivity than the random copolymer or the crosslinked networks at the same composition. Poly(vinyl acetate)-b-polybutadiene-b-poly(vinyl acetate) triblock copolymer was synthesized for water/alcohol pervaporation separation membrane. A difunctional chain transfer agent (dCTA) with both reversible addition - fragmentation chain-transfer (RAFT) and ROMP functionality was synthesized. The triblock copolymers were obtained by synthesizing narrow-dispersed poly(vinyl acetate) by RAFT and subsequently inserting a polybutadiene block by ROMP. The polymers were cast as thin membranes, and the polybutadiene was crosslinked by UV radiation for mechanical robustness. Solid state hydrolysis afforded poly(vinyl alcohol)-b-polybutadiene-b-poly(vinyl alcohol) membranes. Different compositions of the polymers resulted in different morphologies. A longer polybutadiene block or a shorter poly(vinyl alcohol) block contributed to stronger phase separation. This study invented a new methodology to construct amphiphilic triblock copolymers with well-defined morphologies.
Book Synopsis Proton Exchange Membrane Fuel Cells by : David P. Wilkinson
Download or read book Proton Exchange Membrane Fuel Cells written by David P. Wilkinson and published by CRC Press. This book was released on 2009-11-24 with total page 462 pages. Available in PDF, EPUB and Kindle. Book excerpt: A Detailed, Up-to-Date Treatment of Key Developments in PEMFC MaterialsThe potential to revolutionize the way we power our worldBecause of its lower temperature and special polymer electrolyte membrane, the proton exchange membrane fuel cell (PEMFC) is well-suited for transportation, portable, and micro fuel cell applications. But the performance o
Book Synopsis Morphology, Phase Behavior, and Structure/property Relationships of Nylon 6-aromatic Polyimide Graft Copolymers as Potential Molecular Composites by : Chin-Chang Shen
Download or read book Morphology, Phase Behavior, and Structure/property Relationships of Nylon 6-aromatic Polyimide Graft Copolymers as Potential Molecular Composites written by Chin-Chang Shen and published by . This book was released on 1996 with total page 448 pages. Available in PDF, EPUB and Kindle. Book excerpt:
