ELECTRON LOCALIZATION EFFECTS ON THE CONDUCTING STATE IN POLYANILINE

Electron localization effects in polyaniline have been investigated through 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 interpreted as due to the onset of structural order between the chains. This is argued to confirm that the insulator-to-metal transition corresponds to a crossover of the electron states from localization to delocalization. Furthermore, the quasi-one-dimensional variable-range hopping model is shown to account for the observed temperature dependences of the conductivity in the entire protonation range.