TEMPERATURE-DEPENDENCE OF CONDUCTIVITY IN METALLIC POLYACETYLENE

Compiling experimental data on the conductivity of 'metallic' polymers (i.e. those in which the conductivity remains finite in the zero-temperature limit), we distinguish two general types of behaviour: small temperature dependence with a flattening at low temperatures, and larger temperature dependence with increased slope at low temperatures. The first type suggests that there are continuous metallic paths, with conduction limited by regions behaving as disordered metals in parallel with regions involving tunnelling or hopping. The second type is also consistent with this model if there is an additional conductivity term arising from electron-electron interactions, as expected if the disordered metal barrier region is near the metal-semiconductor transition. Our simple heterogeneous model is able to give a good fit to the conductivity temperature dependence of all the samples. © 1990.