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Effect of High Pressure on the Electrical Conductivity of ion Conducting Polymers Prepared for Publication in Electrochim. Acta
Technical rept. 1 Jun 1999-31 May 2000
NAVAL ACADEMY ANNAPOLIS MD DEPT OF PHYSICS
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Complex impedance and differential scanning calorimetry DSC studies have been carried out on polypropylene glycol PPG with an average molecular weight of 1025 and polyethylene glycol mono- methyl-ether PEG with an average molecular weight of 350, both containing NaCF3SO3 in an approximately 201 ratio of polymer to salt. The impedance studies were carried out over a range of frequencies, temperatures and pressures. As expected, PEGNaCF3SO3 exhibits the tendency to crystallize while PPGNaCF3SO3 is a glass-forming liquid. The fit to the zero pressure data for PPGNaCF3SO3 using a recently developed generalized Vogel equation is better than that for the standard VTF equation while for PEGNaCF3SO3 the two expressions give about the same level of fit to the data. In the theory, the critical temperature, Tc, is allowed to vary with pressure. The defect-defect separation is assumed to follow the dimensions of the material. It is found empirically that the pressure dependence of Tc is similar to the pressure dependence of Tg for structurally related polymers containing no salt. Thus, the difference in the pressure dependence of the conductivity for PEGNaCF3SO3 and PPGNaCF3SO3 is attributed primarily to the difference in the pressure dependence of Tg. The details of the relationship between Tc and Tg remain to be determined..
APPROVED FOR PUBLIC RELEASE