Preferential interactions of poly(N‐vinyl‐2‐pyrrolidone) in the binary mixture water/CdCl₂

Abstract

The poly (N-vinyl-2-pyrrolidone)(PVP)(2)/water(1)/CdC1,(3) ternary system has been studied by viscometry, densimetry and atomic absorption spectrophotometry. In this system a preferential adsorption of CdZ+ at all solvent compositions studied and a conformational transition at 4 mM of salt, the concentration at which a preferential adsorption minimum of CdZ+ in exhibited, are observed. The PVP/Cd2+ bound molar ratio is 0.23. CdCl, behaves as a saltingin agent for the macromolecule. The binary solvent mixture is thermodynamically more favourable at salt concentrations greater than 10 mM of CdCl, . K e y words: viscometry, densimetry, unperturbed dimensions, preferential interactions, poly(N-vinyl-2-pyrrolidone), CdCl, .

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

“…Because a linear dependence of on (Lk 2 /Lm 3 ) T, P, m2 is not observed, the function behaviour between 0 m 3 and 5 mM is not known, so the smaller salt concentration studied is used as the lower integration limit. 10 The parameter (Fig. 6B) indicates that the trans-*k 2 fer of energy from water to the salt solution is thermodynamically unfavourable.…”

“…6A solvent system, as the preferential interaction parameter values show. 10 The transfer free energy parameter, expresses *k 2 , the di †erence between the affinities of a macromolecule for the speciÐc solvent system and for pure water. Fitting to the polynomial function :…”