Dielectric studies of hydrogen bonding of aqueous ethylene glycol in a hydrogel

Abstract

The permittivity and loss spectra of a hydrogel of poly(hydroxyethyl methacrylate) containing ethylene glycol aqueous solution have been measured over the frequency range 12 Hz–200 kHz, and the temperature range 77–275 K. The results are compared with the corresponding behaviour of the bulk ethylene glycol solution. The half-width of the spectrum is increased by a factor of two in the hydrogel and the relaxation time by nearly four orders of magnitude, but the calorimetric glass transition temperature (T_g) remains relatively unchanged. The low-temperature, or high-frequency, permittivity is raised from ca. 3.5 to 7.0 which suggests the presence of a second high-frequency relaxation process in the hydrogel. The catastrophic crystallization of the solution is prevented by its incorporation in the hydrogel. These observations are discussed in terms of H bonding and preferential removal of water in the aqueous solution by H-bond interactions with the polymer's network.