Charge transport of the mesoscopic metallic state in partially crystalline polyanilines

Abstract

Charge transport properties, including temperature-dependent dc conductivity, thermoelectric power, electron paramagnetic resonance, microwave frequency dielectric constant and conductivity, and electric-field-dependent conductance of partially crystalline (``physically'' cross-linked) HCl-doped polyaniline correlated with x-ray structure studies, demonstrate that charge delocalization in physically cross-linked polyaniline systems is structurally controlled. Further, we observe a positive dielectric constant at room temperature which increases (to values $g~{10}^{4})$ with increasing percent crystallinity, the size of crystalline regions, and polymer chain alignment in the disordered regions, supporting the establishment of mesoscopic metallic regions. We propose an inhomogeneous disorder model for this system in which ordered (crystalline) regions, described by three-dimensional metallic states, are connected through amorphous regions of polymer chains where one-dimensional disorder-induced localization is dominant. We utilize the metallic box, interrupted metallic strands, and Nakhmedov's phonon-induced delocalization models to account for the temperature dependence of charge transport properties of the various partially crystalline polyanilines. Analyses for the sample and temperature-dependent electron paramagnetic resonance linewidth and thermoelectric power are presented.