Elaboration of ion-exchange membranes with semi-interpenetrating polymer networks containing poly(vinyl alcohol) as polymer matrix

Ion-exchange membranes were prepared with semi-interpenetrating networks (s-IPNs) by mixing a film-forming polymer, poly(vinyl alcohol) (PVA), for the crosslinked matrix and a polyelectrolyte for the specific ion-exchange property. Poly(sodium styrenesulfonate) (PSSNa), poly(styrenesulfonic acid) (PSSH), and poly(acrylic acid) (PAA) were used as anionic polyelectrolytes. Polyethyleneimine (PEI), poly(1,1-dimethyl-3,5-dimethylenepiperidinium chloride) (PDDPCI), and poly(diallyldimethylammonium chloride) (PDDMACI) were used as cationic polyelectrolytes. Membranes with PVA 60% and polyelectrolyte 40% showed the best compromise among mechanical, homogeneous, and ion-exchange properties. Gaseous dibromoethane was used as a crosslinking agent to form the PVA network and for efficient entrapment of the polyelectrolyte in the membrane. The crosslinking time (tc) was optimized for each type of membrane and its influence was studied by thermogravimetric analysis of the sample and scanning electron microscopy observations. The best results (large ion-exchange capacity and small swelling ratio) were obtained for PVA/PAA and PVA/PSSNa/PSSH membranes. Among anion-exchange membranes, PVA/PEI gave the best permselectivity (low co-ion leakage) and the highest ion-exchange capacity, (C) 2002 Wiley Periodicals, Inc.