CONDUCTIVITY OF ORIENTED POLYACETYLENE DOPED BY ALKALI-METALS - TIME,TEMPERATURE, AND PRESSURE-DEPENDENCE

We report the time, temperature, and pressure dependence of conductivi ty of oriented polyacetylene doped by alkali metals. The in situ condu ctivity data show that the doping process, by intercalation, is depend ent on the size and structural ordering of the ions in the polyacetyle ne matrix. Steplike features in the in situ conductivity measurements show the presence of doping-induced staging transitions. The temperatu re dependence of conductivity follows a power law, indicating that the system is at the critical regime of the metal-insulator transition, f or which the Fermi level is near the mobility edge. We find a weaker t emperature dependence for potassium-doped polyacetylene as compared to sodium-doped polyacetylene. The increase of conductivity at high pres sures as well as its weaker temperature dependence shows the important role of the interchain interactions for improving the conductivity of alkali-metal-doped oriented polyacetylene.