Preparation of Amphoteric Ion Exchange Membranes

For type (1), styrene, 2-methyl-5-vinylpyridine and divinylbenzene are copolymerized in the presence of the inert polymer and the obtained membrane is sulfonated and then quartemized 100 amphoteric polyelectrolytes such as a copolymer of jV-diethylamino methacrylate and methacrylic acid are dissolved in a 

For polysalt amphoteric membranes, a cationic polyelectrolyte solution such as poly(benzyl trimethylammonium salt) and an anionic polyelectrolyte solution such as poly(styrene sulfonate) are mixed and a polymer salt precipitated. The polymer salt is then dissolved in a suitable solvent and is formed into a membrane by a casting method.103 

Recently, membranes prepared by a layer-by-layer method have been actively studied. For example, a cationic polyelectrolyte can be adsorbed on a fiat plate as a monolayer and then an anionic polyelectrolyte layer added to it. The same procedure can be repeated, thus forming an ultrathin, multi-layer, amphoteric ion exchange membrane.107 The multi-layers have been formed on a porous membrane in studies on separation membranes108 and, further, such membranes have been studied as new functional materials for sensors, devices for photoelectronics,109 etc. 

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