Polymer-Based Anion Exchangers

Cumbal and Sengupta (2005) produced an effective arsenic removal system by dispersing high-surface area iron (oxy)(hydr)oxide nanoparticles within a base (anion exchange) polymer for permeable matrix support (Table 7.1). The polymer consisted of a quaternary ammonium functional group within a styrene-divinylbenzene matrix. The addition of the nanoparticles improved arsenic removal when compared with the polymer alone. 

The anion-exchange membrane based on polysulfone can be prepared by halo-methylation of the backbone polymer and subsequent reaction with a tertiary amine... 

Pickup PG (1990) Alternating current impedance study of a polypyrrole-based anion-exchange polymer. J Chem Soc Faraday Trans 86 3631-6... 

MAJOR USES Lab reagent chloromethylation monitoring indicator for chloromethyl ether alkylating agent in manufacture of polymers research chemical intermediate in the synthesis of anionic exchange strong base resins of the quartemary ammonium type. 

In the early fifties a number of workers demonstrated the synthesis of homogeneous , high capacity, high conductivity synthetic polymer membranes prepared both by condensation and addition polymerization. Both cation and anion exchange membranes based upon cross-linked polystyrene, reinforced by a fabric mesh became commercially available. 

Yang CC (2012) Alkaline direct methanol fuel cell based on a novel anion-exchange polymer membrane. J Appl Electrochem 42 305-317... 

Mamlouk M, Kumar SM, Gouerec P, Scott K (2011) Electrochemical and fuel cell evaluation of Co based catalyst for oxygen reduction in anion exchange polymer membrane fuel cells. J Power Sources 196 7594—7600... 

The underlying factors behind the selectivity differences between anion-exchange materials based on styrenic and methacrylate monomers are not fully understood. It is likely that these differences can be attributed to the n electrons in the styrenic polymer. Thus, Pohl and Saini [38] were searching for a methodology to synthesize an anion-exchange material free of any k electron character in the polymer backbone. A particularly interesting system for synthesizing a cationic condensation polymer involves the reaction of diepoxides with primary amines. When diepoxides and primary amines are allowed to react in a 1 1 molar ratio, the product is a water-soluble polymer with a predominantly linear architecture. 

Alkaline Membrane Fuel Cells, Membranes, Fig. 4 Scheme of a simplified synthesis of a polyethylene-based anion exchange polymer with quaternary ammonium functional groups... 

It is essential that a solubilized form of an alkaline anion-exchange polymer be developed to improve the interface between the electrodes and the AEM electrolyte. Success in this effort will decrease MEA resistances. A water-based soluble form which can be rendered water insoluble when cast would be preferred, as there are safety concerns (primarily with industrial scale production) about using organic solvents near finely dispersed (pyrophoric) metal catalysts (unsupported or supported on carbon). 

Wang, G., Weng, Y., Chu, D., Xie, D., Chen, R. (2009) Preparation of alkaline anion exchange membranes based on functional poly(ether-imide) polymers for potential fuel cell applications. Journal of Membrane Science, 326, 4—8. 

A flow injection optical fibre biosensor for choline was also developed55. Choline oxidase (ChOX) was immobilized by physical entrapment in a photo-cross-linkable poly(vinyl alcohol) polymer (PVA-SbQ) after adsorption on weak anion-exchanger beads (DEAE-Sepharose). In this way, the sensing layer was directly created at the surface of the working glassy carbon electrode. The optimization of the reaction conditions and of the physicochemical parameters influencing the FIA biosensor response allows the measurement of choline concentration with a detection limit of 10 pmol. The DEAE-based system also exhibited a good operational stability since 160 repeated measurements of 3 nmol of choline could be performed with a variation coefficient of 4.5%. 

Ion exchange resins based on poly(styrene-divinylbenzene) backbones display mixed mode retention mechanisms. The ion exchange functionality (sulfonic acid or carboxylic acid for cation exchangers and quartemary or primary, secondary, or tertiary amines for anion exchangers) contributes to the ionic mechanism and the backbone polymer to hydrophobic retention. This is exemplified... 

A mechanistic study by Haynes et al. demonstrated that the same basic reaction cycle operates for rhodium-catalysed methanol carbonylation in both homogeneous and supported systems [59]. The catalytically active complex [Rh(CO)2l2] was supported on an ion exchange resin based on poly(4-vinylpyridine-co-styrene-co-divinylbenzene) in which the pendant pyridyl groups had been quaternised by reaction with Mel. Heterogenisation of the Rh(I) complex was achieved by reaction of the quaternised polymer with the dimer, [Rh(CO)2l]2 (Scheme 11). Infrared spectroscopy revealed i (CO) bands for the supported [Rh(CO)2l2] anions at frequencies very similar to those observed in solution spectra. The structure of the supported complex was confirmed by EXAFS measurements, which revealed a square planar geometry comparable to that found in solution and the solid state. The first X-ray crystal structures of salts of [Rh(CO)2l2]" were also reported in this study. 

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