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.

Download or read book Structure and Properties of Ordered Block Copolymer Membranes written by Mark Irl Ostler and published by . This book was released on with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

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.

Download or read book Ionomers written by M.R. Tant and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 524 pages. Available in PDF, EPUB and Kindle. Book excerpt: Polymers have achieved an enviable position as the class of materials having the highest volume of production, exceeding that of both metals and ceramics. The meteoric rise in the production and utilization of polymers has been due to advances in polymer synthesis which allow the creation of specific and well-defined molecular structures, to new knowledge concerning the relationships between polymer structure and properties, and to an improved understanding of how processing can be used as a tool to develop morphological features which result in desired properties. Polymers have truly become 'engineered materials' in every sense of the term. Polymer scientists and engineers are forever seeking to modify and improve the properties of synthetic polymeric systems for use in specific applications. Towards this end they have often looked to nature for advice on how to design molecules for specific needs. An excellent illustration of this is the use of noncovalent bonding (ionic, hydrogen, and van der Waals) in lipids, proteins, and nucleic acids, where these noncovalent bonds, acting both intra and intermolecularly, precisely control the structure and thus the function of the entire system. The utilization of ionic bonding, in particular in man-made polymers has attracted widespread interest in recent years, since ionic interactions exert a similar strong influence on the structure and properties of these synthetic systems.

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.

Download or read book Fluorinated Polymers written by Bruno Ameduri and published by Royal Society of Chemistry. This book was released on 2016-10-25 with total page 417 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fluoropolymers display a wide range of remarkable properties and are used in a number of applications including high performance elastomers, thermoplastics, coatings for optical fibers, and hydrophobic and lipophobic surfaces. Fluorinated Polymers: Synthesis, Properties, Processing and Simulation covers the fundamentals of different fluorinated polymers. Topics include the kinetics of homopolymerisation and copolymerization, process chemistry, and controlled radical co-polymerisation techniques. Written by internationally recognized academic and industrial contributors, the book will be of interest to those in industry and academia working in the fields of materials science, polymer chemistry and energy applications of polymers. Together with Fluorinated Polymers: Applications, these books provide a complete overview of different fluorinated polymer materials and their uses.

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.

Download or read book Electrodialysis and Water Reuse written by Andréa Moura Bernardes and published by Springer Science & Business Media. This book was released on 2013-08-30 with total page 144 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents novel techniques to evaluate electrodialysis processes, to synthesize ionic membranes and to characterize their properties. It shows the potential use of membrane process to the treatment of effluents generated in many industrial sectors such as refineries, leather industries, mining and electroplating processes. The book is based on the results obtained by the author's research group during the past decade. It is useful for students, researchers and engineers interested in membrane technologies for water reuse.

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.

Download or read book Polyhedral Oligomeric Silsesquioxane POSS Polymer Nanocomposites written by Sabu Thomas and published by Elsevier. This book was released on 2021-03-25 with total page 578 pages. Available in PDF, EPUB and Kindle. Book excerpt: Polyhedral Oligomeric Silsesquioxane (POSS) Polymer Nanocomposites: From Synthesis to Applications offers extensive coverage of polyhedral oligomeric silsesquioxanes and their nanocomposites, including their synthesis, characterization, interfacial interactions and advanced applications. Sections introduce essentials, information on their preparation and discussions on polymeric materials, including elastomers, thermoplastics, thermosetting polymers, polymer blends and IPNs. Further sections cover the latest analysis techniques, examine the properties of POSS-polymer nanocomposites, and discuss key application areas, such as biological, energy, defense, and space. Finally, issues surrounding industry implementation and lifecycle are explored. This is a valuable reference for researchers, scientists and advanced students in the areas of polymer composites and nanocomposites, polymer chemistry, polymer physics, polymer science, and materials science and engineering. In an industrial setting, this book will be of great interest to scientists, R&D professionals, and engineers across industries and disciplines. Covers all aspects of polyhedral oligomeric silsesquioxanes (POSS) and their nanocomposites, including synthesis and characterization techniques, properties, analysis, applications and trends Targets POSS nanocomposites, describing synthesis, characterization and the selection of POSS filler types according to polymeric material Explains the preparation and utilization of POSS polymer nanocomposites for cutting-edge applications, including biological, energy, and defense field applications

Download or read book Chemical Abstracts written by and published by . This book was released on 2002 with total page 2730 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Publications of the National Institute of Standards and Technology Catalog written by National Institute of Standards and Technology (U.S.) and published by . This book was released on 1991 with total page 480 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Directory of Graduate Research written by American Chemical Society. Committee on Professional Training and published by . This book was released on 2005 with total page 1932 pages. Available in PDF, EPUB and Kindle. Book excerpt: Faculties, publications and doctoral theses in departments or divisions of chemistry, chemical engineering, biochemistry and pharmaceutical and/or medicinal chemistry at universities in the United States and Canada.

Download or read book Publications written by United States. National Bureau of Standards and published by . This book was released on 1991 with total page 480 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Coulombic Interactions in Macromolecular Systems written by Adi Eisenberg and published by Washington, D.C. : The Society. This book was released on 1986 with total page 288 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book American Doctoral Dissertations written by and published by . This book was released on 2002 with total page 776 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Dissertation Abstracts International written by and published by . This book was released on 2002 with total page 684 pages. Available in PDF, EPUB and Kindle. Book excerpt: