Microwave dielectric response of mesoscopic metallic regions and the intrinsic metallic state of polyaniline

We report the dependence of the microwave-frequency dielectric constant and dc conductivity on the crystallinity and local order of doped polyaniline. The dramatic increase of the dielectric response in the three highest crystalline physically crosslinked polyaniline samples provides evidence for the formation of three-dimensional coupled mesoscopic metallic regions. We report the measurement of a negative dielectric constant in polyaniline (doped with camphor sulfonic acid) demonstrating the intrinsic metallic nature of polyaniline.