Hydration water dynamics in solutions of hydrophilic polymers, biopolymers and other glass forming materials by dielectric spectroscopy

Abstract

Broadband dielectric spectroscopy (10^−2 Hz–10^6 Hz) and differential scanning calorimetry measurements have been performed to study the molecular dynamics of several water solutions in the water concentration region from 30 wt% to 50 wt% and in the temperature range from 140 to 250 K. The analysis of the dielectric data in these water solutions revealed an universality in the temperature dependence of the relaxation times at temperatures lower and higher than the calorimetric glass transition (Tg). At temperatures lower than Tg, an universal Arrhenius behaviour with an average activation energy of (0.54 ± 0.10) eV is obtained, whereas at temperatures higher than Tg an universal VFT (Vogel-Fulcher-Tamman) behaviour is found.