Synthesis and electrical properties of NaSS–MAA–MMA cation exchange membranes for membrane capacitive deionization (MCDI) Original Research Article

We present a novel synthetic ion exchange membrane that is composed of 4-styrenesulfonic acid sodium salt hydrate (NaSS), methacrylic acid (MAA) and methyl methacrylate (MMA), which was synthesized with various monomer ratios using solution polymerization. The ion exchange membrane was prepared by heat cross-linking and esterification reactions. The chemical structure of the membrane was characterized using Fourier-transform infrared (FT-IR) and nuclear magnetic resonance (NMR) spectroscopy. Several membrane properties were measured, including water uptake, ion exchange capacity (IEC), ion transport number and electrical properties. The morphology analysis of the membrane was also obtained by scanning electron microscope (SEM). Increasing the NaSS concentration simultaneously increased the IEC and the electrical conductivity due to the increased presence of ionic groups. Compared with conventional membranes, the pattern of cyclic charge and discharge currents in the synthetic membrane indicated that it possessed more efficient electrosorption and desorption properties.