VISCOSITY BEHAVIOR OF POLY(N-VINYL-2 PYRROLIDONE) IN A WATER VOSO4 BINARY MIXTURE - PREFERENTIAL INTERACTIONS/

Poly(N-vinyl-2-pyrrolidone) (PVP) [2]/water [1]/VOSO4 [3] ternary syst em interactions have been studied by viscometric and densitometric tec hniques. Preferential water absorption inside the macromolecular coil and preferential salt interaction with the polymer external domain wer e observed. The unperturbed dimensions of the macromolecule increased with the salt concentration up to 75 mM VOSO4, a point where the intri nsic viscosity was also a maximum and a conformational transition coul d be produced. The polymer-solvent interaction became worse with salt concentration and VOSO4 behaved as a salting-in agent for the polymer, the binary solvent mixture being thermodynamically unfavourable.