Modification of transport properties of ion exchange membranes, XIII. Surface‐modified cation exchange membranes prepared from polyamines and a copolymer membrane containing p‐stryenesulfonyl chloride

A membrane precursor was prepared by the copolymerization of p‐styrenesulfonyl chloride and divinylbenzene in the presence of a poly(vinyl chloride) supported cloth. The surface of the membrane was treated with various amines, and then the sulfonyl chloride groups in the internal part of the membrane were hydrolyzed with an aqueous sodium hydroxide solution in organic methanol or acetone solvent. Hydrolysis conditions were examined for the introduction of the sulfonic acid groups. The membrane modified by ethylenediamine exhibited slightly bipolar properties during the electrodialysis of seawater. Surface‐modified membranes using tetraethylenepentamine exhibited excellent monovalent cation permselectivity, low membrane electric resistance, and long performance durability during the electrodialysis of seawater.