Preparation and characterization of a cation exchange membrane using a styrene-hydroxyethyl acrylate-lauryl methacrylate terpolymer

Abstract

A novel cation exchange membrane based on a styrene-hydroxyethyl acrylate-lauryl methacrylate terpolymer (St-HEA-LMA) was prepared. Sulfonic groups were introduced to the membrane structure with sulfuric acid as the sulfonating agent and silver sulfate as the initiator. Sulfonated St-HEA-LMA terpolymer membranes were characterized by Fourier-transform infrared (FTIR) spectroscopy and atomic force microscopy (AFM), as well as by determining the degree of sulfonation (DS), ion-exchange capacity (IEC), swelling ratio and electrical resistance of the membranes. The presence of sulfonic groups in the sulfonated St-HEA-LMA terpolymer was confirmed by FTIR, and the resulting membrane exhibited an ion-exchange capacity of 2.13 meq/g and an electrical resistance of 1.17 Ω·cm2. The swelling ratio of the prepared membranes increased with increasing degree of sulfonation, and the tensile strength decreased with increasing degree of sulfonation at a reaction temperature of 30°C. The phase images obtained by AFM clearly showed an increase in roughness with increasing DS. Considering the mechanical properties, the sulfonated St-HEA-LMA terpolymer obtained at a sulfonation reaction temperature of 20°C was suitable for ion-exchange membrane applications.