COMPLEX CONDUCTIVITY OF POLYACETYLENE FILMS PREPARED BY DIFFERENT METHODS

The frequency (f) and temperature (T) dependence of the complex conductivity sigma* was measured for undoped and lightly doped films of highly stretchable polyacetylene (hs-PA) and Shirakawa polyacetylene (S-PA). When sigma* and f were reduced by using the dc conductivity sigma(0), all the experimental data of sigma* of hs-PA were on a master curve whereas those of S-PA did not show such universality. The data analysis based on the conductivity relaxation formalism revealed that the functional form H(tau) is-proportional-to tau-alpha (tau(min) < tau < tau(max), -1 < alpha < 1) of the relaxation spectrum H(tau), i.e., the distribution function of relaxation time tau, fitted the experimental data best and that alpha was independent of T for hs-PA while alpha was proportional to T for S-PA. The T-independent alpha for hs-PA indicates isoenergetic hopping between equivalent sites, so that the conduction mechanism in hs-PA can be ascribed to acoustic-phonon-assisted hopping of charged solitons between PA chains. On the other hand, it is likely that the inter-fibril-barrier hopping makes the main contribution to the conduction mechanism in S-PA. This difference in conduction mechanisms between hs-PA and S-PA is attributed to their morphological dissimilarities.