Determination of the interaction parameter between vinyl alcohol and vinyl acetate in PVAc

Polyvinylalcohol, PVA, is an increasingly important industrial material used for water-soluble unit dose applications. Vinyl alcohol cannot be directly polymerised; therefore PVA is prepared by the hydrolysis of polymerised vinyl acetate, PVAc. For most applications the PVA is incompletely hydrolysed and the residual acetate groups while not inherently hydrophilic help to suppress crystallisation and render the copolymer more soluble. Remarkably, we can find no direct measure of the compatibility of PVAc and PVA in the literature, but this is important to understand in order to predict the solubility and interdiffusion behaviour of the material. We propose to use SANS to study well-defined blends of deuterium-labelled P-dVAc with PVAc of the same degree of polymerisation but somewhat different degrees of hydrolysis. These experiments will provide detail structural analysis of PVAc in the melt state as well as the interaction parameter between VA and VAc groups.