The volumetric behaviour of poly(vinyl alcohol) in aqueous solution

Abstract

High-precision density measurements of aqueous solutions of a narrow molecular mass fraction of poly(vinyl alcohol) prepared by 80% alcoholysis of poly(vinyl acetate), over an extended range of concentration and temperature, have revealed a complex pattern of solution behaviour. The concentration dependence of the partial molal volume and apparent molal expansibility indicate that two processes occur in solution; a conformational change at low concentrations (ca. 0.05% w/w) and an aggregation at higher concentrations (ca. 0.2% w/w). The concentration at which these processes occur varies with temperature showing a minimum in the region 14–18 °C. The volumetric data presented suggest that the temperature dependence of these two processes is a function of the solvent–solvent interactions and the minimum at 14–18 °C reflects a critical region for water over this temperature range.