ELECTRON LOCALIZATION EFFECTS ON THE CONDUCTING STATE IN POLYANILINE

Electron localization effects in polyaniline have been investigated th rough the dependence of DC conductivity and magnetic susceptibility on thermal aging. A dramatic effect of thermal aging on conductivity is reported in the insulator-to-metal transition region, which is interpr eted as due to the onset of structural order between the chains. This is argued to confirm that the insulator-to-metal transition correspond s to a crossover of the electron states from localization to delocaliz ation. Furthermore, the quasi-one-dimensional variable-range hopping m odel is shown to account for the observed temperature dependences of t he conductivity in the entire protonation range.