Effect of molecular structure of hybrid precursors on the performances of novel hybrid zwitterionic membranes

Abstract

Three types of novel hybrid zwitterionic membranes were prepared via a coupling reaction between two silane-coupling agents in a nonaqueous system and a subsequent reaction with 1,4-butyrolactone to create ion pairs in the hybrid precursors. FT-IR spectra corroborated the corresponding reactions. The synthesized membranes were characterized by thermal analyses, ion-exchange capacities, streaming potentials, and pure water flux. Thermal analyses exhibited that the degradation temperature of the hybrid precursors decreased with an increase in zwitterionic extent because of the introduction of ion pairs. Ion-exchange capacity measurements revealed that the anion-exchange capacities and cation-exchange capacities were in the range of 0.023–0.05 and 0.32–0.58 mmol g−1, respectively. Streaming potentials displayed that when the membranes coated for one or three times, the isoelectric points were in the pH range of 6.6–7.58 and 6.58–7.7, respectively. The pure water flux showed that it could be affected by the coating times and the ingredients of these zwitterionic membranes. This difference in membrane's characteristics can be ascribed to the effect of molecular structure of the hybrid precursors. Both the Coulombic interactions of ion pairs between the polymer chains and the hydrophilicity of these membranes were proposed to clarify the above phenomena. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007