Study of charge transport in highly conducting polymers based on a random resistor network

Based on a random resistor network (RRN), we study the unusual ac conductivity sigma (omega) of highly conducting polymer such as PF6 doped polypyrrole. The system is modeled as a composite medium consisting of metallic regions randomly distributed in the amorphous parts. Within the metallic regions, the polymer chains are regularly and densely packed, outside which the poorly arranged chains form amorphous host. The metallic grains are connected by resonance quantum tunneling, which occurs through the strongly localized states in the amorphous media. sigma (omega), calculated from this model, reproduces the main experimental features associated with the metal-insulator transition in these polymers. (C) 2004 Elsevier B.V. All rights reserved.