NMR, DCS, TMA, and High Pressure Electrical Conductivity Studies in Solid, Crosslinked Dimethylsiloxane-Ethylene Oxide Copolymer Networks Containing Sodium.
NAVAL ACADEMY ANNAPOLIS MD DEPT OF PHYSICS
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Audio frequency electrical conductivity and 23Na NMR studies have been carried out on solid, crosslinked dimethylsiloxane-ethylene oxide copolymer networks containing sodium. The electrical 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 exhibits VTF or WLF behavior. From a VTF analysis, Ea is found to be about 0.11 eV and T sub 0 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 KGP and Ea 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 cu cmmol over the temperature range 262-323K. The 23Na 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 23Na line above room temperature suggests the possible presence of ion pairs or higher aggregates in the complex. Keywords Solid electrolytes Polymer electrolytes.
- Physical Chemistry