Water in Hydrogels Studied by Dielectric, Thermal and Water Sorption/Diffusion Techniques

Abstract

Several results obtained by the authors in recent years in the investigation of polymer–water interactions and of the state of water in hydrogels based on poly(hydroxyethyl acrylate) (PHEA) are briefly reviewed and discussed. The systems investigated include PHEA homopolymers, composites and interpenetrating polymer networks (IPNs). The techniques employed for the investigation include density measurements, water sorption/diffusion techniques, differential scanning calorimetry (DSC), broadband dielectric relaxation spectroscopy (DRS) and thermally stimulated depolarization currents (TSDC) techniques. The composites and the IPNs are microphase-separated systems and the PHEA fraction in them behaves essentially like pure PHEA. Several correlations, as well as distinct differences, were observed and discussed between the results obtained by the various techniques. The combination of the dielectric DRS and TSDC techniques makes dielectric aquametry a powerful tool for investigations of hydrogels.