Inhomogeneous disorder and the modified Drude metallic state of conducting polymers

The metallic state of the very highly conducting doped polymers, such as polyacetylene, polypyrrole and polyaniline, is shown to have remarkable similarities. Though each of these doped polymers has a different temperature-dependent conductivity, each of these doped polymer systems has a similar metal-like Pauli susceptibility and density of states at the Fermi level. Also, each of these highly conducting systems displays a universal electronic response (dielectric constant and conductivity) as a function of frequency from the microwave regime (10⁹ Hz) through to the 'all conduction electron plasma frequency' (1 to 3 eV, depending on the polymer). This common behavior despite apparent differences in the temperature-dependent conductivities is proposed to be a consequence of the inhomogeneous crystalline order in these materials, leading to three-dimensional metallic domains or islands (crystallographically coherent regions), separated by poorly conducting weak links (disordered regions and interfiber links).