Diffusion coefficients of conductive ions in a copolymer of vinylidene cyanide and vinyl acetate obtained from dielectric measurements using the model of Trukhan

Abstract

[EN] The dielectric dispersion measurements of Furukawa et al.(4) are treated in the light of a previously proposed model of Trukhan.(6) The latter describes the influence of mobile ions on the dielectric dispersion in a slab of material placed between polarizable electrodes. It is shown that the so-called ''constant phase element'' is just a crude approximation to the predictions of the theory of Trukhan, an approximation not valid at very low frequencies. At low frequencies macropolarizations appear analogous to the ones observed in asymmetric cellulose acetate membranes by Malmgren-Hansen et al.(11) The polarizations are much larger in the present case, and this indicates that there are no microheterogeneities in the polymeric film of Funikawa et al.(4) The diffusion coefficient of the most rapidly diffusing ion (presumably Hf) may be found as a function of temperature within some uncertainty. The Arrhenius plot shows clearly the change in activation energy around the glass transition temperature (182 degrees C). Below the glass transition the activation energy for diffusion is much larger (similar to 50000 K) than above. The diffusion coefficients increase from similar to 10(-17) m(2)/s at 170 degrees C to similar to 5.10(-16) m(2)/s at 195 degrees C. The concentration of electrolyte present in the polymer increases from similar to 15 to similar to 200 mol m(-3) in the same temperature interval. (C) 1996 American Institute of Physics.