Modification of the transport properties of ion exchange membranes. IX. Layer formation on a cation exchange membrane by acid-amide bonding, and transport properties of the resulting membrane

Abstract

In order to modify the transport properties of sulfonic acid-type cation exchange membranes, chlorosulfonyl groups were introduced as reactive groups into the membrane composed of a styrene-divinylbenzene copolymer and poly (vinyl chloride) fabric. The chlorosulfonated membrane was then reacted with various amino compounds. Suitable reaction conditions of the copolymer membrane with chlorosulfonic acid were examined in detail. After the chlorosulfonated membrane had been immersed in an aqueous solution of amino compounds to form a different kind of layer by acid amide bonding, mainly on the membrane surface, the membrane was immersed in aqueous sodium hydroxide solution to hydrolyze unreacted chlorosulfonyl groups to sodium sulfonate groups. The amino compounds used were p-aminosalicylic acid, L-tyrosine and polyamino compounds such as triethylenetetramine, polyethyleneimines etc. Formation of the polyamino compound layer on the surface of the cation exchange membrane by acid amide bonding conferred stable monovalent cation permselectivity on the membrane in electrodialysis. All reactions were confirmed by measurements of attenuated total reflectance infrared spectra.