Study on the graft of 4-vinyl pyridine to styrene-butadiene-styrene triblock copolymer by solution polymerization shows that the catalyst concentration, temperature, and reaction time are the major influencing factors. Graft efficiency increases with temperature and time but levels off when temperature is higher than 65°C. Increasing concentration of catalyst also promotes graft, but when it is higher than 1.0 × 10−2M, the reaction system begins to gel.
A cast film of the graft copolymer was dried, cross-linked with S2Cl2 in nitromethane solution, sulfonated, and chloromethylated. The water content of the membrane is 13.5%. Its anionic and cationic exchange capacities are 0.066 mEq per dry gram and 0.273 mEq per dry gram, respectively. The anionic-cationic capacity ratio is thus 0.26.
The nitrogen content of the graft copolymers was determined with a CHN elemental analyzer, and qualitative analysis was carried out with infrared spectroscopy. Transmitting electronic microscopy was used to study the morphology and feasibility of preparing a charged mosaic membrane for piezodialysis.