Synthesis And Characterization Of Polymeric Anion Exchange Membranes

Synthesis And Characterization Of Polymeric Anion Exchange Membranes
Author: Wenxu Zhang
Publisher:
Total Pages:
Release: 2016
Genre:
ISBN:

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As alkaline anion exchange membrane fuel cells (AAEMFC) are regarded as promising and important energy devices, the development of high performance anion exchange membranes are in urgent need, as well as fundamental investigation on the structure-property relationship, which are the motivation of this dissertation. Three different polymer systems are presented and focused on polymer synthesis, material morphology, and ion transport phenomena. Crosslinked membranes are promising as practical materials, however, the understanding and further improvement of its performance is hindered by the lack of an ordered morphology or well-defined chemical structure. In Chapter 2, a series of crosslinked membranes were design to bear cationic groups organized via covalent linkages, which were synthesized by sequential reversible addition-fragmentation chain transfer radical polymerization (RAFT), "click" chemistry, cast/crosslinking process, and solid state quaternization. Significant enhancement in conductivities was observed and presumably attributed to the formation of ion transport channels directed by polycation chains. Excellent membrane performance were observed, including conductivities, water diffusivities, and fuel cell power densities. In Chapter 3, phosphonium containing block copolymers were synthesized and subjected to morphology characterization. Using Small Angle X-ray Scattering (SAXS) and Transmission Electron Microscopy (TEM), it was observed that these materials form well-ordered morphologies upon solvent casting, and the ionic block preferred to form a continuous phase. By comparing the anion conductivities, the matrix in a hexagonal phase was proved to be more efficient in ion transport than lamellae. Polycyclooctene (PCOE) based triblock copolymers were synthesized in Chapter 4, by using a special chain transfer agent (CTA) to mediate Ring-Opening Metathesis Polymerization (ROMP) and reversible addition-fragmentation chain transfer radical polymerization (RAFT). The well-defined melting transition (~50 oC) of PCOE enabled the investigation of the thermal transition in hydrophobic block affecting ionic domain behavior. Then metal ion doped star block copolymers were investigated in bulk and thin film forms to demonstrate that the star block copolymer architecture can facilitate microphase separation and thus the preparation of smaller features. Using an ortho-nitrobenzyl ester junction, triblock copolymers based on PEO and PSt were synthesized and applied to hierarchical pattern fabrication in self-assembled thin films. During these studies, the single monomer insertion methodology was developed for high efficiency synthesis of (multi)functional RAFT CTAs. The molecular characterization and controlled polymerization results were documented in Chapter 7. The last chapter contains outlooks based on the research in this dissertation. Methods to improve the previously presented materials were listed. Also, fundamental questions were raised on ion transport membranes, and possible ways to answer them were provided. In addition, potential research directions are proposed.

Ion Exchange Membranes

Ion Exchange Membranes
Author: Toshikatsu Sata
Publisher: Royal Society of Chemistry
Total Pages: 325
Release: 2007-10-31
Genre: Science
ISBN: 1847551173

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Various separation membranes have been developed since their discovery over half a century ago, providing numerous benefits and fulfilling many applications in our everyday lives. They lend themselves to techniques ranging from microfiltration and gas separation, to what can be considered as the most advanced technique - ion exchange. This book, aimed at academic researchers, engineers and industrialists, contains a brief history of ion exchange and goes on to explain the preparation, characterization, modification and applications of these important membranes. Discussions include the use of ion exchange in analytical and medical techniques, as well as the development of future applications.

Synthesis and Characterization of Phosphonium-Containing Cationic Poly(styrene) Polymers

Synthesis and Characterization of Phosphonium-Containing Cationic Poly(styrene) Polymers
Author:
Publisher:
Total Pages: 14
Release: 2009
Genre:
ISBN:

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Alkaline fuel cells have been proposed as a cost effective alternative energy solution due to their cheap manufacture and low operating temperatures. Their mass utilization, however, is hindered by their electrolyte material. While relatively inexpensive solid proton exchange membranes have been available for some time now, alkaline fuel cells still rely on liquid electrolyte to provide mobility to the anionic species. In this technical note, we describe an ionomeric system designed as an anion exchange membrane for these types of applications. Styrene monomer has been copolymerized with 4-vinylbenzyltrimethylphosphonium chloride to produce several statistical copolymers via reversible addition-fragmentation chain transfer (RAFT) polymerization, a controlled radical polymerization method. The synthetic approach and preliminary results are discussed, as well as future plans.

Ion Exchange Membranes

Ion Exchange Membranes
Author: Tongwen Xu
Publisher: John Wiley & Sons
Total Pages: 437
Release: 2024-03-11
Genre: Science
ISBN: 3527841431

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Ion Exchange Membranes A comprehensive introduction to the electro-membrane technologies of the future An ion exchange membrane is a polymer-based membrane which can be permeable by some ions in a solution while blocking others, making them ideal for processes such as water desalination, salt concentration control, clean production and—given their electrical conductivity—power generation and energy storage etc. Recent advances have given rise to new electro-membrane processes that promise drastically to expand the applications of this technology. Scientists in both research and industry will increasingly need to draw on these membranes in vital ways with strongly positive potential environmental impact. Ion Exchange Membranes summarizes recent research into these membranes and electro-membrane processes before moving to an overview of the historical background. It then attends in detail to cutting-edge fabrication technologies and the most recent areas of use. The result is a comprehensive introduction to the design, fabrication, and applications of these increasingly essential membranes. Ion Exchange Membranes readers will also find: In-depth treatment of industrial-scale applications Detailed discussion of topics including side-chain engineering, polyacylation, superacid-catalyst polymerization, and more Analysis of electro-membrane processes such as alkaline membrane water electrolysis, solar-driven water splitting, and many more Ion Exchange Membranes is ideal for membrane scientists, materials scientists, inorganic chemists, polymer chemists, and researchers and engineers in a variety of fields working with ion exchange membranes and electro-membrane processes.

Polymeric Membrane Synthesis, Modification, and Applications

Polymeric Membrane Synthesis, Modification, and Applications
Author: Chandan Das
Publisher: CRC Press
Total Pages: 390
Release: 2018-10-12
Genre: Science
ISBN: 0429998783

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Membranes and membrane separation techniques have grown from a simple laboratory tool to an industrial process with considerable technical and commercial impact. The book deals with both the fundamental concepts of preparation, characterization and modification, practical applications along with recent advancements of electro-spun and phase inverted polymeric membranes. Divided into two parts, part one of this book covers the fundamental concepts and practical applications of novel electro-spun membranes while the latter covers basic concepts and further advancements of the conventional phase inverted membranes extensively. Key Features Covers fundamental concepts and practical applications of electro-spun and phase inverted polymeric membranes Includes general properties, characterization, preparation and modification of polymeric membranes Discusses advanced modification of polymeric membranes (functionalization, grafting) using phase inversion process, and effects of solubility parameter and additives on the phase inversion process Reviews electro-spun membranes for biomedical applications, industrial effluents treatment and removal of water contaminants Explores a separate economic analysis section for the discussed membranes

Enhancements of the Synthesis and Fabrication of Anion Exchange Membranes

Enhancements of the Synthesis and Fabrication of Anion Exchange Membranes
Author: Megan Matta
Publisher:
Total Pages: 0
Release: 2023
Genre:
ISBN:

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Ion exchange membranes (IEMs) have emerged as important components in a wide variety of electrochemical processes and applications, playing a vital role in facilitating the selective transport of ions while preventing species crossover between the anolyte and catholyte. These versatile polymer or polymer composite membranes find uses in diverse fields such as energy conversion and storage, water treatment, chemical synthesis, and biotechnology. At the core of their functionality, ion exchange membranes exhibit a unique property known as "selective permeability." This property allows them to permit the controlled movement of specific ions across their structure based on differences in charge and size, while restricting the transport of other species. Diffusion of other molecules, such as water, can also be controlled simultaneously by optimizing the ion content, water uptake, and polymer structure of these materials. The design and synthesis of ion exchange membranes involve the incorporation of charged functional groups capable of exchanging ions with the surrounding solution. This functional group can be embedded in the backbone of the polymer, in an ionene-type structure, or attached to the backbone by tethered side chains. IEMs are broadly classified by the charge of the functional group into cation exchange membranes (CEMs) and anion exchange membranes (AEMs). CEMs have anionic functional groups and permit the transport of cations, whereas AEMs have cationic functional groups and permit the transport of anions. Bipolar membranes (BPM) are a type of composite IEM consisting of an AEM and CEM laminated together and an interesting topic of future research. Most AEMs produced today contain chemically unstable arylene ether backbones, have poor mechanical properties, and require toxic reagents for functionalization. This dissertation seeks to synthesize new anion exchange membranes that are stable in alkaline conditions while maintaining the high conductivities required for the operation of electrochemical devices. To develop a chemically stable aliphatic polyolefin AEM, a library of polymers synthesized via Ziegler-Natta polymerization was examined. This library consisted of quaternized poly(11-bromo-1-undecene-co-4-phenyl-2-butene) with degrees of functionalization of 20 mol% to 50 mol% -- and was made utilizing a different catalyst system than previously explored. A TiCl3ˑAA catalyst was reacted with triisobutylaluminum (TiBA) co-catalyst to synthesize a more robust catalyst complex than the traditional AlEt2Cl catalyst. It was found that this new system could incorporate a higher amount of halogenated monomer (up to 50 mol %) on a multi-gram scale (50 g) at high yield without poisoning and deactivating the catalyst. The monomer incorporation was equal to the monomer feed and allowed for the targeting of specific ion exchange capacities. A large-scale synthesis (100 g) was conducted to assess the feasibility of pilot scale experiments. The dissolved polymers were solvent cast onto an ePTFE support and heterogeneously quaternized by immersing the alkylbromide-functionalized membrane in trimethyl amine solution. This procedure resulted in uneven wrinkled membranes, and a new method of casting supported membranes was subsequently developed, as described below. The hydroxide conductivity of the membranes was measured at room temperature, with conductivities up to 32 mS/cm reported. Given the issues with deformities in the supported membranes, further work focused on developing more efficient and consistent methods of membrane fabrication. It is speculated from initial experiments that high molecular weight polymer was being filtered from the sample during solution processing -- decreasing the mechanical strength of cast membranes. The quaternary ammonium-functionalized polyolefins were cryomilled to retain high molecular weight polymer without aggregation. Casting membranes from the cryomilled powder increased the mechanical properties of the membrane such that the mechanical membrane support was no longer needed. Moreover, cryomilling facilitated bulk heterogenous quaternization of the polymer prior to membrane fabrication, reducing the amount of trimethylamine solution needed. Attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) measurements confirmed that the Menshutkin reaction went to completion and all bromine moieties were quaternized for all degrees of functionalization. The quaternized polymer resins were cryomilled to yield a free-flowing powder that could be used for AEM fabrication. The polymers were examined with thermogravimetric analysis, and the degradation temperature of the ammonium was found to be 215 °C in the chloride form. Suggesting that thermal processing, such as heat pressing, is a viable option for membrane fabrication. Environmentally benign ethanol as a solvent was utilized to disperse the powder and cast membranes unsupported. The resulting AEMs were smooth, with even appearance across the sample, and thin, with thicknesses ranging between 15 [mu]m and 20 [mu]m. Preliminary synthesis on a monomer for ring opening metathesis polymerization (ROMP) was attempted in an effort to examine the effects of well-defined backbone architecture on conductivity and chemical durability. The monomer, 3-(N,N'-dimethylpropyl-1-amine)-cyclooctene, was synthesized in high purity and characterized by proton NMR. Unfortunately attempts to polymerize the monomer via ROMP were unsuccessful as of the writing of this dissertation.

Ionomers

Ionomers
Author: M.R. Tant
Publisher: Springer Science & Business Media
Total Pages: 524
Release: 2012-12-06
Genre: Technology & Engineering
ISBN: 940091461X

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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.

Ion Exchange Membranes

Ion Exchange Membranes
Author: Tongwen Xu
Publisher: John Wiley & Sons
Total Pages: 437
Release: 2024-05-28
Genre: Science
ISBN: 3527351949

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Ion Exchange Membranes A comprehensive introduction to the electro-membrane technologies of the future An ion exchange membrane is a polymer-based membrane which can be permeable by some ions in a solution while blocking others, making them ideal for processes such as water desalination, salt concentration control, clean production and—given their electrical conductivity—power generation and energy storage etc. Recent advances have given rise to new electro-membrane processes that promise drastically to expand the applications of this technology. Scientists in both research and industry will increasingly need to draw on these membranes in vital ways with strongly positive potential environmental impact. Ion Exchange Membranes summarizes recent research into these membranes and electro-membrane processes before moving to an overview of the historical background. It then attends in detail to cutting-edge fabrication technologies and the most recent areas of use. The result is a comprehensive introduction to the design, fabrication, and applications of these increasingly essential membranes. Ion Exchange Membranes readers will also find: In-depth treatment of industrial-scale applications Detailed discussion of topics including side-chain engineering, polyacylation, superacid-catalyst polymerization, and more Analysis of electro-membrane processes such as alkaline membrane water electrolysis, solar-driven water splitting, and many more Ion Exchange Membranes is ideal for membrane scientists, materials scientists, inorganic chemists, polymer chemists, and researchers and engineers in a variety of fields working with ion exchange membranes and electro-membrane processes.