THE POLY(VINYL ALCOHOL) BORATE SYSTEM - INFLUENCE OF POLYELECTROLYTE EFFECTS ON PHASE-DIAGRAMS

The formation of a reversible gel by complexation of berate ions with poly(vinyl alcohol) is described. The complexation induces electrostat ic charges on the polymeric chains. We focus on the behaviour of the s ystem when the charges are partially screened by a passive salt. In su ch a case, 're-entrant phases' can be observed; they result from a del icate balance between the electrostatic repulsions among charged compl exes formed on the polymeric chain and the crosslinking induced by ber ate ions. We present here an interpretation of the phase transitions b ased on a thermodynamic approach.