Viscosity Behaviour of Poly(N-vinyl-2-pyrrolidone) in a Water/VOSO4Binary Mixture: Preferential Interactions

Poly(N-vinyl-2-pyrrolidone) (PVP) [2]/water [1]/VOSO4 [3] ternary system interactions have been studied by viscometric and densitometric techniques. Preferential water absorption inside the macromolecular coil and preferential salt interaction with the polymer external domain were observed. The unperturbed dimensions of the macromolecule increased with the salt concentration up to 75mM VOSO4, a point where the intrinsic viscosity was also a maximum and a conformational transition could 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.