METALLIC BEHAVIOR IN HIGHLY CONDUCTING POLYMERS

We give a brief review of transport data in highly conducting polymers and suggest specific microscopic and macroscopic pictures that can account for the data. The conductivity temperature dependence of new polyacetylene is generally consistent with a combination of Sheng's expression for fluctuation-induced tunnelling and highly anisotropic metallic conduction, with a maximum intrinsic conductivity exceeding 10(6) S/cm. Despite the high conductivity, localization effects sometimes to occur at low temperatures: these could be due to charging energy effects in interchain transfer at low temperature, or to quantum corrections as in disorders metals. The surprisingly linear thermopower observed for new polyacetylene argues against conduction models involving a change in the number of charge carriers with temperature. It also indicates a smaller interaction between electrons and phonons than in normal metals, which is consistent with the remarkably high intrinsic conductivities inferred.