Polymer–water interactions in PAA hydrogels

Abstract

Polymer–water interactions in poyacrylamide (PAA) hydrogels were investigated by means of broad-band dielectric relaxation spectroscopy (DRS, 10 −2–10 6 Hz) and of thermally stimulated depolarization currents (TSDC) techniques (77–300 K) at several hydration levels. The critical water content for the saturation of primary hydration sites was determined to be h c=0.15 (dry basis). For water contents h> h c plasticization effects dominate the behaviour of hydrogels. Two further critical water contents were determined from TSDC measurements at subzero temperatures related to freezing of water and to reorganization of water in the hydrogels, respectively. The activation energy of DC protonic conductivity was determined to be 0.8±0.1 eV at h=0.25.