Dielectric study of aqueous solutions and solid samples of methylcellulose

Abstract

The dielectric properties of aqueous solutions and hydrated solid samples of methylcellulose were studied by means of the thermally stimulated depolarization current (TSDC) method in the temperature range 77–300 K and over a wide range of concentrations, 0.025–2.0 gr/lt, and water contents, 1.8–34.9%. Two water-dependent complex dispersions were observed in the range of 77–155 K (low-temperature dispersion) and 155–300K (high-temperature dispersion). The high-temperature dispersion was studied in detail. In the solutions the dispersion is due to thermal release of space charges trapped at the boundaries of the crystallites of the polycrstalline samples. In the solid samples three mechanisms contribute to the dispersion: water-assisted relaxation of local polar groups, space charge polarization connected with dc conductivity and accumulation of space charges at the electrodes. The results allow us to determine the critical water content for the completion of the primary hydration layer to 7–8 %.