SOLUTION PROPERTIES OF POLY(VINYLPYRROLIDONE) IN COSOLVENT SYSTEMS

For solutions of well fractionated poly(vinylpyrrolidone) (PVP) sample s of different relative molar mass M, intrinsic viscosities [eta] have been measured at 298.15 K in pure water and water/acetone mixtures. U pon mixing water (good solvent) and acetone (poor solvent), thermodyna mically better solvents could be obtained. The cosolvancy was detected from the viscosity measurements. Several graphical procedures have be en utilized for deriving the unperturbed dimensions of PVP expressed a s K(theta) (in the relationship [eta] = K(theta)M1/2alpha3, where alph a is the expansion factor). It was found that the unperturbed dimensio ns were not constant and differed from those measured in the theta-sol vent (water/acetone mixture having volume fraction of acetone (theta(A CT)) = 0.668) in which K(theta) was found to be 74 x 10(-3) dm3 kg-1. A solvent-dependent parameter has been utilized to correct the K(theta ) values derived from Stockmayer-Fixman plot, in each solvent, for the sake of achieving a constant value of K(theta) via these plots. Value s ranging between 73 x 10(-3) and 75 x 10(-3)dm3 kg-1 with a mean of 7 4 x 10(-3) dm3 kg-1 were obtained by utilizing the proposed correction , thus yielding 0.666 angstrom g-(1/2) mol1/2 for unperturbed polymer dimensions, ([r2]0/M)1/2.