Synthesis and properties of an anion-exchange membrane based on vinylbenzyl chloride–styrene–ethyl methacrylate copolymers

Novel synthetic ion-exchange membranes composed of 4-vinylbenzyl chloride, styrene, and ethylmethacrylate were synthesized by radical polymerization using various monomer ratios. Copolymers with the desired molecular weights were successfully synthesized (Mn>39.5×103 g/mol, Mw>52.8×103 g/mol). After the radical polymerization, the ion-exchange membranes were prepared through amination and heat curing. The chemical structures of the membranes were characterized using Fourier-transform infrared spectroscopy and 1H and 13C nuclear magnetic resonance spectroscopy. The thermal, electrical, and other basic properties of the membranes, including water uptake and ion-exchange capacities, were measured. The glass temperature values of the polymers ranged from 67.5 to 81.2 °C. The nitrate permeation properties were also investigated by applying the membranes in a capacitive deionization system. Compared to conventional membranes, the nitrate concentrations in the cyclical charge and discharge currents indicated that the synthesized membranes were more efficient.