Elaboration of a membrane with bipolar behaviour using the semi-interpenetrating polymer networks technique

The semi-interpenetrating polymer network technique was applied for the elaboration of three ion-exchange membranes. Poly(vinyl alcohol) (PVA) was chosen as polymer matrix. Commercial poly(styrene sulfonate) (PSSNa) was used as anionic polyelectrolyte (Pe). Poly(N-ethyl-4-vinylpyridinium bromide) (PEVPBr) and poly(vinylpyridinium chloride) (PVPCI) were synthesised and characterised in order to use them as cationic Pe. Membranes were obtained by mixing PVA and Pe solutions, followed by solvent evaporation and crosslinking with gaseous 1,2-dibromoethane. The influence of the crosslinking conditions on the sample properties was studied. Various processes were used to elaborate the bipolar membranes (BMs). The most interesting result was obtained by sticking together a wet PVA/PEVPBr membrane on a wet PVA/PSSNa membrane using a PVA/PSSH (acidic form of PSSNa) solution as glue and by crosslinking the junction by heat treatment. Current-voltage experiments were performed on the BMs. Bipolar behaviour was observed when a water dissociation catalyst was introduced in the PVA/PEVPBr layer. (C) 2002 Elsevier Science Ltd. All rights reserved.