Preparation and characterization of ion-exchange membrane using Sty/HEA/LMA terpolymer via post-sulfonation

An ion-exchange membrane based on a styrene/hydroxyethyl acrylate/lauryl methacrylate (Sty/HEA/LMA) terpolymer was prepared via a post-sulfonation reaction for various sulfonation times. Sulfonic groups were introduced into the membrane structure with sulfuric acid as the sulfonating agent and silver sulfate as an initiator. Sulfonated Sty/HEA/LMA membranes were characterized by Fourier transform infrared spectrometry (FT-IR) and nuclear magnetic resonance (NMR), as well as by determining the degree of sulfonation (DS), ion-exchange capacity (IEC), water uptake (WU) and electrical property of the membranes. The presence of sulfonic groups in the sulfonated Sty/HEA/LMA membranes was confirmed by FT-IR, and the resulting membrane showed an ion-exchange capacity of 0.812 meq/g and an electrical resistance of 0.3 Ω cm2. Water uptake of the prepared membranes increased with the degree of sulfonation at the reaction time. The surface morphology obtained by AFM clearly showed an increase of roughness with sulfonation reaction time. The elongation of the Sty/HEA/LMA ion-exchange membranes were improved with the increasing LMA content compared to sulfonated polystyrene membrane.