Novel hollow‐fiber anion‐exchange hybrid membranes: Preparation and characterization

To develop ion‐exchange membranes for application in severe conditions, such as those with high temperatures, strongly oxidizing environments, or organic solvents, new hollow‐fiber anion‐exchange hybrid membranes were prepared by the immersion of brominated poly(2,6‐dimethyl‐1,4‐phenylene oxide) base hollow fibers in a tetraethoxysilane–ethanol solution followed by sol–gel and quaternary amination. Compared to conventional polymeric charged membranes, the prepared hybrid membranes were higher in both thermal and dimensional stabilities. The results suggest that tetraethoxysilane concentration was an important factor affecting the membrane's intrinsic properties. When the tetraethoxysilane concentration was in the range 15–45%, the final hollow‐fiber anion‐exchange hybrid membranes had an ion‐exchange capacity of 1.9–2.0 mmol/g, a water uptake of.83–1.23 g of water/g of dry weight, and a dimensional change ratio of 13–18%. An evaluation on the membranes' separation performances is underway. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Chitosan-Modified Poly(2,6-dimethyl-1,4-phenylene Oxide) for Anion-Exchange Membrane in Fuel Cell Technology

A series of cross-linking chitosan-modified quaternary ammonium poly(2,6-dimethyl-1,4-phenylene oxide)s membranes (CS-QAPPO) were prepared by the Menshutkin reaction. The mechanical property, dimensional stability, and alkaline stability of the CS-QAPPO membrane have been impressively improved by introducing CS into PPO backbone. Even the hydroxide conductivity of CS-QAPPO membranes is higher than that of the pristine QAPPO membrane. The 20% chitosan-modified QAPPO membrane shows the best performance, and the hydroxide conductivity is 32 mS cm^?1 at 90°C. The alkaline stability measurements demonstrated excellent chemical stability of the CS-QAPPO membrane in 2?M NaOH solution at room temperature after 2,000?h.     

Novel anion exchange membranes having fluorocarbon backbone: Preparation and stability

Anion exchange membranes with excellent durability were prepared by chemical modification of Nafion. The modification was achieved by transformation of the sulfonic acid group into quaternary ammonium group. Namely, Nafion membrane was first converted into an amide-type membrane. Reduction of the carbonxyl group to methylene followed by quaternarization with alkyl iodide resulted in the formation of an anion exchange membrane. The electric resistance of the resulting membranes depends on the equivalent weight of the starting membranes (4.4–6.0 Ω cm² in 0.5N NaCl). The characteristics of the membranes are the excellent stability toward chemical substances such as organic solvents, oxidizing agents, acids, etc. For example, the membranes are stable in aqueous saturated chlorine solution at 60°C for 1000 hr.     

The origin and elimination of water splitting in ion exchange membranes during water demineralisation by electrodialysis

Water splitting in anion exchange membranes containing quaternary ammonium groups is due to the presence of tertiary alkyl amino groups in the surface regions. It may be eliminated by methylation, however it reappears during current flow because quaternary ammonium groups in the surface regions are then converted to the tertiary form. The quaternary ammonium groups are more stable in Negev Institute A than in AMF A1OO membranes. By contrast water splitting is not manifested by cation exchange membranes with sulphonic acid groups if the system is sufficiently clean.     

Quaternized poly(phenylene oxide) anion exchange membrane for alkaline direct methanol fuel cells in KOH‐free media

A series of anion exchange membrane (AEM) electrolytes with quaternary ammonium moiety are fabricated from poly (phenylene oxide) for its application in alkaline direct methanol fuel cells (ADMFCs). In the first step, poly(phenylene oxide) (PPO) is successfully chloromethylated by substituting chloromethyl groups in the aryl position of polymer. In the second step, the chloromethylated PPO (CPPO) is further homogeneously quaternized and ion‐exchanged to form an AEM. From the second step, series of AEMs are prepared by changing the mole ratio of amine in relation to CPPO. The presence of quaternary ammonium group in the membrane was confirmed by elemental analysis. The fabricated membranes are subjected to cell polarization studies in ADMFCs, wherein quaternized poly(2,6‐dimethyl‐1,4‐phenylene oxide) (CPPO:amine of 1:8) membrane exhibits higher peak power density of 3.5 mW cm^?2 when compared with the other ratios of CPPO:amine in the absence of KOH solution. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43693.     

Imidazolium functionalized poly(vinyl alcohol) membranes for direct methanol alkaline fuel cell applications

In this study, imidazolium functionalized poly(vinyl alcohol) (PVA) was synthesized by acetalization and direct quaternization reaction. Afterwards, composite anion exchange membranes based on imidazolium‐ and quaternary ammonium‐ functionalized PVA were used for direct methanol alkaline fuel cell applications. ¹H NMR and Fourier transform infrared spectroscopy data indicated that imidazole functionalized PVA was successfully synthesized. Inductively coupled plasma mass spectrometry data demonstrated that the imidazolium structure was efficiently obtained by direct quaternization of the imidazole group. Composite anion exchange membranes were fabricated by application of the functionalized PVA solution on the surface of porous polycarbonate (PC) membranes. Fuel cell related properties of all prepared membranes were investigated systematically. The imidazolium functionalized composite membrane (PVA‐Im/PC) exhibited higher ionic conductivity (7.8 mS cm^?1 at 30 °C) despite a lower water uptake and ion exchange capacity value compared to that of quaternary ammonium. In addition, PVA‐Im/PC showed the lowest methanol permeation rate and the highest membrane selectivity as well as high alkaline and oxidative stability. Dynamic mechanical analysis results reveal that both composite membranes were mechanically resistant up to 10⁷ Pa at 140 °C. The superior performance of imidazolium functionalized PVA composite membrane compared to quaternary ammonium functionalized membrane makes it a promising candidate for direct methanol alkaline fuel cell applications. © 2020 Society of Chemical Industry     

Crosslinked anion exchange membrane with improved membrane stability and conductivity for alkaline fuel cells

As a core component of anion exchange membrane (AEM) fuel cells, it has practical significance to improve the performance of AEMs. However, it is difficult to obtain AEM with both good stability and high conductivity. In this study, a series of AEMs were prepared by chloromethylation, quaternization, and crosslinking reactions. The quaternization reaction was carried out first to ensure that there are abundant quaternary ammonium groups on AEM and enhance the conductivity of membrane. N,N,N′,N′-tetramethylethylenediamine was used as a crosslinker to improve membrane stability and mechanical property. A simple, mild, and cost-effective AEM synthetic route was developed. This strategy achieves a certain balance of electrochemical and physical properties. The effect of the crosslinking reactions on the property of membrane was evaluated. Crosslinked membranes have better dimensional stability (water uptake: 20.2% and swelling ratio: 2.1%), mechanical properties (55.84 MPa), and alkaline stability because crosslinked structures result in large steric hindrance. The mutually independent quaternization and crosslinking reaction do not affect the electrochemical performance of membranes; in the crosslinking reaction stage, crosslinker also reacted as quaternization agent and increased the number of reactive groups in AEM. Thus, the resulting crosslinked AEM exhibits higher ion exchange capacity and ionic conductivities (46.4 mS cm⁻¹). © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48169.     

Preparation of anion exchange membranes based on pyridine functionalized poly(vinyl alcohol) crosslinked by 1,4-dichlorobutane

A series of anion exchange membranes [pyridine functionalized-poly(vinyl alcohol)-1,4-dichlorobutane (PVA-PY-DL_x)] were synthesized by using PVA-PY as polymer matrix and DL as crosslinker and iodomethane as quaternization reagent. During the experiment, pyridine groups grafted on PVA were transformed into quaternary ammonium group during the formation process of the crosslinked structure and the quaternization routine by iodomethane. The characterization results revealed that the PVA-PY-DL_x membranes have been successfully prepared and the crystallinity increases with increase of DL. PVA-PY-DL_x membranes have smooth and uniform morphology. The introduction of crosslinked structure improves the mechanical properties and dimensional stability of the PVA-PY-DL_x membrane, enhances the alkali resistance. When the mass content of DL was 4.0%, composite membrane had the maximum tensile strength (44.2 MPa), and the OH⁻ conductivity reaches 1.05 × 10⁻² S cm⁻¹ at 70 °C. The accelerated aging experiment was carried out in 3 mol L⁻¹ potassium hydroxide (KOH) solution for 120 h at 80 °C, which revealed that the anionic conductivity of PVA-PY-DL_4.0 membrane retains 79.6% of its initial conductivity, showing better stability of alkali stability. Methanol permeability of PVA-PY-DL_x membranes was only the 0.37–0.72% of the Nafion-117 membrane in 3 mol L⁻¹ methanol at 60 °C. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47395.     

Synthesis of polymer‐supported quaternary ammonium salts and their phase‐transfer catalytic activity in halogen‐exchange reactions

Polymer‐supported quaternary ammonium salts were prepared, and their applications as phase‐transfer catalysts in aqueous organic systems were investigated. The polymer‐bound phase‐transfer catalysts were prepared with polystyrene resins crosslinked with the bifunctional monomers divinylbenzene and 1,4‐butanediol dimethacrylate. The polymers were functionalized with chloromethyl groups and quaternized with trialkylamines having different alkyl chains. The obtained phase‐transfer catalysts were characterized with IR spectroscopy and elemental analysis. The thermal stability was also determined by the thermogravimetric method. The catalytic properties of the phase‐transfer catalysts were studied in halogen‐exchange reactions. The effects of the nature and extent of crosslinking of the polymer support, the alkyl groups of the trialkylamine, and the reaction conditions were investigated. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci 2009     

Anion‐Exchange Membranes for Fuel Cells: Synthesis Strategies,Properties and Perspectives

This review focuses on various synthesis strategies of anion‐exchange membranes (AEMs) for fuel cells, diverse methodologies of AEM‐forming, together with relationship between structures and properties. AEMs are discussed from seven categories, including (1) AEMs derived from Nafion precursors with sulfonyl fluoride groups, which display excellent stability and well‐developed morphologies that similar to Nafion, but has potentially high costs. (2) AEMs prepared by grafting technologies, such as chemical grafting technique, ATRP technique, plasma grafting technique and radiation grafting technique. (3) AEMs based on functionalized commercial polymers, including PVA, SEBS, CPP, PEEK, PES, PEI, PPO, and so on. (4) AEMs prepared by newly‐synthesized polymers, in which the most interesting approach is to synthesize alkaline multi‐block copolymers with enough long hydrophilic/hydrophobic blocks. (5) AEMs containing heterogeneous composition, which mainly prepared by blending and sol‐gel methods, reinforced or pore‐filling AEMs and IPN or s‐IPN. (6) AEMs with functional groups different from quaternary ammonium, which includes the studies of new type of AEMs with highly chemical stability in alkaline solution. (7) Hybrid membranes combining AEM with PEM, in which new configuration results in different performances. At last, conclusions and perspectives for the future researches of AEMs are presented.     

Anion exchange membranes derived from nafion precursor for the alkaline fuel cell: Effect of cation type on properties

Highly stable hydroxide conducting membranes are necessary for solid‐state alkaline fuel cells to have long performance lifetimes. In this study, we used solid‐state chemistry to synthesize Nafion‐based anion exchange membranes (AEMs) with a variety of covalently attached cations, including trimethylammonium, trimethylphosphonium, piperazinium, pyrrolidinium, pyridinium, and quaternized 1,4‐diazabicyclo[2.2.2]octane. Infrared spectroscopy confirms a partial asymmetric functionalization of all cations with the exception of pyridinium. The AEMs that were successfully synthesized all exhibited sufficient water uptake and conductivity. The effect of cation type on AEM chemical and thermal stability was investigated as a function of various conditions (e.g., hydration levels, temperature, and pH). High chemical and thermal stability was observed for all successfully synthesized AEMs with the exception of the trimethylphosphonium cation AEM. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Sternpolymere als funktionale Bausteine für neuartige Nanofiltrationsmembranen

Interest in thin‐film membranes with properties specially tailored to the respective separation process is growing. In order to obtain such membranes with high permselectivity and fouling resistance, established membrane systems are combined with new building blocks. Star polymers are a class of promising building blocks. In this study, star polymers with anion exchange groups of variable molecular weight and low polydispersity were synthesized by atom transfer radical polymerization. The anion exchange groups were tertiary amino and quaternary ammonium groups. The resulting star polymers were integrated into polyamide thin‐film composite membranes using interfacial polymerization.     

Synthesis and thermal stability of novel anion exchange resins with spacer chains

Spacer-modified anion exchange resins were prepared by suspension copolymerization of ω-bromoalkylstyrenes or ω-bromoalkyloxymethylstyrenes with 2–8 mol % of divinylbenzene, followed by quaternization with trimethylamine. The thermal stability of the spacer-modified anion exchangers of the OH form was examined by standing the resins in deionized water at 100–140°C for 30–90 days. The anion exchangers with alkylene chains such as butylene or heptylene groups between the benzene ring and the quaternary nitrogen exhibited higher thermal stability compared with commercial, strongly basic anion exchangers with benzylic ammonium groups. The thermal stability of the exchangers with butyleneoxymethylene or hexyleneoxymethylene spacers was also higher than that of the commercial exchangers. The exchanger with the propyleneoxymethylene spacer, however, had less stability than did the commercial ones. The decreased stability of this spacer-modified exchanger is due to the accelerated degradation of the spacer chain via Hofmann elimination. The excellent stability of the anion exchangers with alkylene or alkyleneoxymethylene spacers, except propyleneoxymethylene, results from the structure of the exchangers, where there are no reactive benzylic carbons, which are attached directly to the quaternary nitrogen. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 1161–1167, 1997     

Development of quaternarized poly(vinyl alcohol) anion‐exchange membranes for applications in electrodialysis

The main objective of this work is the development of anionic exchange membranes for the treatment of solutions containing metallic ions using the electrodialysis process. Anionic membranes were synthesized from poly(vinyl alcohol), with the insertion of quaternary ammonium groups in the polymeric matrix and subsequent crosslinking with glutaraldehyde and maleic anhydride. Different membranes were synthesized in order to evaluate the combination of physical–chemical properties and ionic transport. The morphology and structure of the membranes were investigated by scanning electron microscopy and infrared spectroscopy. The thermal transitions and stability of all the membranes were characterized using calorimetric techniques: thermogravimetric analysis, and differential scanning calorimetry, and compared with those of the individual polymers. The physical properties (ion‐exchange capacity, water absorption, and dimensional stability) showed that the different crosslink agents used significantly affect the membrane properties. The electrodialysis performance of the membranes in the transport of chloride and nitrate ions showed that the membranes produced can be successfully used in this separation process. Selemion® AMV commercial membrane was used to compare the percentage extractions of the indicated ions with the produced membranes. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44946.     

Effect of styrene addition on chemically induced grafting of 4‐vinylbenzyl chloride onto low‐density polyethylene for anion exchange membrane preparation

Anion exchange membranes were prepared from graft polymerization of 4‐vinylbenzyl chloride on low‐density polyethylene matrix and subsequent amination with trimethylamine solution. The graft polymerization was initiated by benzoyl peroxide instead of gamma ray radiation. The resulting membranes had insufficient anion exchange functional groups; however, this could be enhanced by adding 10% styrene to 4‐vinylbenzyl chloride in a graft polymerization reaction. Further addition of styrene resulted in a decrease of the ion exchange capacity of anion exchange membranes due to competition with 4‐vinylbenzyl chloride in graft polymerization onto polyethylene. These were evidenced by analytical titration, elemental analysis, infrared spectroscopy and ¹H NMR. © 2019 Society of Chemical Industry     

Charged polyacrylonitrile membranes having amphiphilic quaternized ammonium groups for ultrafiltration

Four types of positively charged polyacrylonitriles having quaternized N,N-dimethylaminoethyl methacrylate (DAMA) were synthesized and were used to prepare ultrafiltration membranes by a phase-inversion method. The effect of aliphatic ethyl, octyl, and stearyl groups and the benzyl group, which covalently bind to the quaternary ammonium group, on filtration properties was studied by ultrafiltration under an applied pressure of 760 mmH₂O. Water permeability through the resultant membranes increased as the aliphatic chain length on the quaternary ammonium group increased. For a copolymer membrane having a benzyl group on the quaternary ammonium group, water permeability was lower than that for the ethyl type of copolymer membrane. The membrane permeability and pore size for the molecular size-exclusion effect were studied at various NaCl concentrations in the 0–0.15M region. The membranes having octyl and stearyl groups showed stable filtration behavior by increase of the NaCl concentration, while the membranes having an ethyl group and a benzyl group on the quaternary ammonium group showed a change of the water permeability due to a pore-size increase for the membrane by NaCl addition. Measurements of membrane potential indicated the shielding of positively charged sites of the membranes by salt addition. Further, the copolymer membranes showed a separation ability for water/2-butanol of low water content. The separation ability was attributed to the chemical structure of the membranes having different interaction characteristics with the mixture components. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 1821–1828, 1998     

Preparation of anion exchange membrane based on homogeneous quaternization of bromomethylated poly(arylene ether sulfone)

This article presented the synthetic and preparation route of quaternary ammonium functionalized anion exchange membranes (AEMs), which were derived from an engineering plastics polymer, poly(arylene ether sulfone) with 3,3′,5,5′‐tetramethyl‐4,4′‐dihydroxybipheny moiety (PAES‐TM). The benzylmethyl groups on the main‐chain of PAES‐TM were converted to the bromomethyl groups via a radical reaction, thereby avoiding complicated chloromethylation, which required carcinogenic reagents. The chemical structure of the bromomethylated PAES was characterized by ¹H NMR spectrum. Following a homogeneous quaternization with trimethylamine in the solution, a series of flexible and tough membranes were obtained by a solution casting and anion exchange process. The ion exchange capacity values were ranging from 1.03 to 1.37 meq g^?1. The properties of the membranes, including water uptake, hydroxide conductivity, and methanol permeability were evaluated in detail. The AEM showed a high conductivity above 10^?2 S cm^?1 at room temperature and extremely low methanol permeability of 4.16–4.94 × 10^?8 cm² s^?1. The high hydroxide conductivity of TMPAES‐140‐NOH could be attributed to the nano‐scale phase‐separated morphology in the membrane, which was confirmed by their transmission electron microscopy images. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40256.     

Investigation on structure and properties of anion exchange membranes based on tetramethylbiphenol moieties containing copoly(arylene ether)s

Quaternary ammonium functionalized poly(arylene ether)s (QPAEs) containing 2,2′,6,6′‐tetramethylbiphenol moieties were designed and successfully synthesized via nucleophilic substitution polycondensation, bromination, quaternization and alkalization. The structure, water uptake, ion exchange capacities (IECs), hydroxide ion conductivities, and mechanical properties, as well as thermal and chemical stabilities of obtained QPAEs membranes were investigated. The QPAE‐a membrane with IEC value of 0.98 meq g^?1 demonstrated the highest ion conductivity (47.4 mS cm^?1) at 80°C. The ion transport activation energy (E_a) of QPAEs membranes varied from 8.57 to 19.95 kJ mol^?1. After chemical stability test conditioned in 1M NaOH at 60°C for 7 days, the QPAEs membranes except QPAE‐c (IEC = 0.88 meq g^?1) still exhibited high hydroxide ion conductivities (over 15 mS cm^?1) and acceptable tensile strength (～10 MPa). These properties indicate that the ionomers membranes are potential candidates for anion exchange membranes in anion exchange membrane fuel cells. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41525.     

Fluorenyl‐containing Quaternary Ammonium Poly(arylene ether sulfone)s for Anion Exchange Membrane Applications

A series of anion exchange membranes (AEM) based on block quaternary ammonium poly(arylene ether sulfone) (QA‐bPAES) were successfully synthesized from 9,9′‐bis(4‐hydroxyphenyl) fluorene, 4,4′‐(hexafluoroisopropylidene) diphenol and 4,4′‐difluorodiphenyl sulfone via block polymerization, chloromethylation, quaternization, alkalization and solution casting. Properties of the obtained QA‐bPAES membranes, including ion exchange capacity (IEC), water uptake, swelling ratios, methanol permeability and ion conductivity were investigated. The obtained QA‐bPAES membranes showed low water uptakes, high ion conductivities and good physical and chemical stability. For example, the membrane of QA‐bPAES(20/10)‐1.34 with IEC of 1.34 mmol g⁻¹ exhibited swelling ratios of 5.0% and 5.1% in in‐plane and through‐plane direction, respectively, and ion conductivity of 15.6 mS cm⁻¹ in water at 60 °C with low methanol permeability of 1.06 × 10⁻⁷ cm² s⁻¹ (25 °C). All the results indicated that this type of block membranes had good potentials for alkaline anion exchange membrane fuel cell applications.     

非硫光气法合成一些难合成的芳基异硫氰酸酯

在三乙烯二胺存在下，芳胺与二硫化碳反应先生成芳胺基二硫代甲酸盐，然后与双(三氯甲基)碳酸酯(BTC)反应，可用于制备苯环上连接了硝基、三氟甲基或者两个以上卤素等吸电子基团的难合成芳基异硫氰酸酯，收率达到71％～95％。