Interaction between water and polymer chains in poly[hydroxyethyl acrylate) hydrogels

Polymer networks of different cross-linking densities were prepared by copo lymerisation of hydroxyethyl acrylate and ethylene glycol dimethacrylate. T he average molecular weight between cross-links as well as the polymer chai n mobility were characterised by means of dynamic-mechanical spectroscopy. Equilibrium sorption iso-therms and the water uptake in immersion in liquid water allowed the determination of the Flory-Huggins interaction parameter between water molecules and polymer chain segments, which decreased with t he water activity in the hydrogel and increased with the crosslinking densi ty as a consequence of the hydrophobic character of the cross-linking agent . Dynamic sorption and desorption experiments were used to determine the di ffusion coefficient.