| A systematic charge transport study was performed to investigate charge localization and delocalization phenomena in hydrochloride and camphor sulfonic acid doped polyaniline materials. The study of the dependence of charge transport on crystallinity and local order of doped polyaniline indicates that the charge delocalization is structurally controlled by the volume fraction of crystalline regions and by the degree of local order in the crystalline and amorphous regions. Microwave dielectric response and crystalline domain coherence length obtained from x-ray scattering experiments provide valuable information to distinguish between three different delocalization regimes: uncoupled metallic islands, a coupled "mesoscopic" metallic state, and an intrinsic metallic state. At low temperature, the dielectric constant is proportional to the square of the crystalline domain coherence length for both parallel and perpendicular directions, establishing that the metallic state of doped polyaniline is three dimensional. The dramatic increase of the microwave dielectric constant in high crystalline hydrochloride doped polyaniline provides evidence for the formation of three dimensional coupled "mesoscopic" metallic regions. The negative dielectric constants of camphor sulfonic acid doped polyaniline in m-cresol solvent and a center portion of stretched, heavily doped polyacetylene indicate the existence of intrinsic metallic state. |
