Hopping electron transport in doped polyaniline: An experimental verification of the Fogler–Teber–Shklovskii model

We present a systematic study of the temperature (T) dependence of the dc electrical conductivity of own-made polyaniline pellets doped over a wide range. The dopant is dodecylbenzenesulfonic acid, except for two samples that are fully doped with HCl. A crossover between low-T variable-range hopping and high-T nearest-neighbor hopping has been found below room temperature for most of the samples, which is atypical for conducting polymers. This allows us to construct a diagram that relates various regimes in the hopping electron transport to disorder level and T. Our experimentally constructed diagram closely resembles that proposed theoretically by Fogler, Teber, and Shklovskii for the hopping transport in coupled chain-like conductors in the presence of Coulomb interaction. This implies that the model is applicable to conducting polymers if Coulomb interaction is not negligible.