Incompatibility of polyelectrolyte solutions — mixed solutions of PSSNa and PVSNa

The compatibility of PSSNa and PVSNa in aqueous solution has been studied. PSSNa and PVSNa are compatible when the total concentration is less than 1.0 mol/l, but phase separation occurs when the total concentration exceeds 1.0 mol/l. The cloud point curve is of a typical UCST type. Addition of salt causes a shift of the boundary toward a lower concentration. It may be considered that these new critical phenomena are a reflection of the balance between electrostatic and non-electrostatic interactions. The time evolving processes of the phase separation has also been investigated. The characteristic behavior of spinodal decomposition is observed when the temperature of a mixed solution is jumped down passing through the critical point.