Solution Properties of Poly(vinylpyrrolidone) in Cosolvent Systems

Abstract

For solutions of well fractionated poly(vinylpyrrolidone) (PVP) samples of different relative molar mass M, intrinsic viscosities [η] have been measured at 298.15 K in pure water and water/acetone mixtures. Upon mixing water (good solvent) and acetone (poor solvent), thermodynamically better solvents could be obtained. The cosolvancy was detected from the viscosity measurements. Several graphical procedures have been utilized for deriving the unperturbed dimensions of PVP expressed as Kθ (in the relationship [η]=KθM1/2α3, where α is the expansion factor). It was found that the unperturbed dimensions were not constant and differed from those measured in the θ-solvent (water/acetone mixture having volume fraction of acetone (φACT)=0.668) in which Kθ was found to be 74×10−3 dm3 kg−1. A solvent-dependent parameter has been utilized to correct the Kθ values derived from Stockmayer-Fixman plot, in each solvent, for the sake of achieving a constant value of Kθ via these plots. Values ranging between 73×10−3 and 75×10−3 dm3 kg−1 with a mean of 74×10−3 dm3 kg−1 were obtained by utilizing the proposed correction, thus yielding 0.666 Å g−(1/2) mol1/2 for unperturbed polymer dimensions, (〈r2〉0/M)1/2.