NMR, DSC, TMA, and High Pressure Electrical Conductivity Studies in Solid, Crosslinked Dimethylsiloxane-Ethylene Oxide Copolymer Networks Containing Sodium

摘要

Audio frequency electrical conductivity and Sodium 23 NMR studies have been carried out on solid, crosslinked dimethylsiloxane-ethylene oxide copolymer networks containing sodium. The measurements have been carried out in vacuum over the temperature range 5-380K and at pressures up to 0.65 GPa over the temperature range 230-380K. The electrical conductivity for the complexed material and the electrical relaxation time associated with the alpha relaxation in the uncomplexed material exhibit VTF or WLF behavior. From a VTF analysis of the electrical conductivity, E sub a is found to be about 0.11 eV and T sub o is found to be about 45 C below the central glass transition temperature as determined by both DSC and TMA. Also, T sub o is found to increase about 50 KI/GPa and E sub a increases significantly with pressure. In addition, the high pressure studies show that the activation volume associated with the electrical conductivity decreases from 44 to 23 cc/ml over the temperature range 262-323K. The Sodium NMR measurements reveal the presence of both bound and mobile sodium species, the relative concentrations of which change by about a factor of 10 over the temperature range -100 to +100 C. Broadening of the bound Sodium line above room temperature suggests the possible presence of ion pairs or higher aggregates in the complex.