Preparation and characterizations of novel zwitterionic membranes

A novel route was proposed for preparation of zwitterionic membranes, and it comprises (1) free radical polymerization between glycidylmethacrylate (GMA) and acrylic acid (AA) monomers and (2) subsequent ring-opening of epoxide and quaternary amination with trimethylamine hydrochloride. The reaction products were confirmed by FTIR spectra. The cation-exchange capacities (CIECs) and anion-exchange capacities (AIECs) of these zwitterionic membranes are within the range of (5.4–9.3) × 10−2 and (30.6–11.1) × 10−2 mmol g−1, respectively. In addition, the CIEC increases as AA content increases, but the AIEC generally decreases. TGA and DrTGA measurements reveal that their thermal stabilities can arrive at as high as 380 °C. The water uptake is independent of pH. As for membrane potential and streaming potential, they both suggest that these membranes possess the characteristics of anion-exchange membranes and no IEP is observed. Permeation experiments of mixed KCl and glucose solution indicate that the transport behavior of ions is dependent on the membrane’s charge density.