Studies on Viscosity of PVP in Mixed Solvents H2O/THF

The dilute solution viscometer is used to research the ternary solution of Poly（N-vinylpyrrolidone） （PVP） in mixed solvents H2O/ THF. H2O is the good solvent of PVP，and THF the non-solvent. The viscometric study indicates that the intrinsic viscosity η of PVP may be higher in the mixed solvents than in the pure solvent H2O and change with the variation of the volume fraction of THF，Ф. It is found that at first η increases slowly and then decreases rapidly with the adding of THF. A maximum value of η appears at Ф20. 3，which decreases after the adding of Na2SO4，but the value of Ф，at which the maximum value of η appears，varies relatively little. The change in values of η and coil dimensions in mixed solvents are discussed in terms of the molecular characteristics of the system and intermolecular interactions，especially in terms of the form of new structure—clathrate hydrate structure，and the relative influence upon the nature of solvent. It is stated that the properties of ternary systems （polymer / mixed solvent）might not be deduced directly from those of the binary systems composed of each component liquid.