Fundamental studies of novel inorganic-organic charged zwitterionic hybrids 4. New hybrid zwitterionic membranes prepared from polyethylene glycol (PEG) and silane coupling agent

A series of novel hybrid zwitterionic membranes were prepared via a coupling reaction of trimethoxysilyl functionalized polyethylene glycol (PEG) and zwitterionic process with 1,4-butyrolactone (BL) thereafter. Both Fr-IR and C-13 NMR spectra confirmed the step reactions. Thermal analysis shows that the weight loss of the hybrid zwitterionic copolymer decreased slightly compared with the non-ionization hybrid precursor and the thermal stability of such zwitterionic copolymer can reach around 240 degrees C. Streaming potentials display that whether the membranes were coated once or thrice, they always exhibit negative values and no isoelectric point (IEP) was found in the tested pH range. Ion exchange capacities (IECs) reveal that only the cation-exchange capacities (CIECs) were detected and the CIECs of the membranes coated one to four times were in the region of (1.9-2.5) x 10(-2) mequiv. cm(-2). Pure water flux shows that it can be affected by the coating times and the substrate. The SEM images suggest that substrates can influence the membrane's microstructures. The increasing electrostatic repulsion between ion pairs and the pendent side structure of polymer chains might be responsible for these unusual behaviors. (c) 2006 Elsevier B.V. All rights reserved.