Ionic membranes for water desalination. I. Charge mosaic membranes from blends of random copolymers

Abstract

AbstractThe incompatibility of polymers was used in order to prepare films with regular phase separation. The conversion of the separate phases into polyelectrolytes of different charge should lead to the preparation of charge mosaic membranes for piezodialysis.Copolymers of suitable monomers with 20–45 mole‐% butadiene content were synthesized which could be cross‐linked with sulfur monochloride. The comonomers were: styrene, 2‐vinyl pyridine, 4‐vinyl pyridine, methacrylic acid, methyl methacrylate and 2‐chloroethyl methacrylate.After conversion into the ionic form cross‐linked films of these copolymers showed salt rejections in the range of 26–78 % and water permeabilities of 40–43 [1· mm· m−2· day−1], respectively. These films can be used as anion and cation exchange membranes for water desalination.Mixtures of poly (2‐vinyl pyridine‐co‐butadiene) and poly (styrene‐co‐butadiene) yielded films with regular phase separation. After cross‐linking and conversion into the ionic form these charge mosaic membranes were porous and had poor mechanical strength. Despite these unfavourable properties a salt enrichment of 4.8 % was found in one case.