Observation of crossover from three- to two-dimensional variable-range hopping in template-synthesized polypyrrole and polyaniline

Electronically conductive polymers can be synthesized within the pores of microporous membranes to yield microscopic tubules of the polymer. We have investigated the temperature dependence of resistance of thin films prepared from microtubules composed of polyaniline and polypyrrole. All resistance data obtained followed the Mott variable-range hopping (MVRH) model. However, films prepared from large-diameter tubules (400 nm) showed three-dimensional (3D) MVRH, while films prepared from small-diameter tubules (\ensuremath{\le}100 nm) showed 2D MVRH. Hence, we have demonstrated the ability to reproducibly vary the dimensionality of conduction in a conductive polymer film.