Despite nearly three decades of materials development, the transport properties in the 'metallic state' of the so-called conducting polymers are still not typical of conventional metals1, 2, 3, 4, 5, 6, 7. The hallmark of metallic resistivity—a monotonic decrease in resistivity with temperature—has not been obtained at temperatures over the full range below room temperature; and a frequency dependent conductivity, (), typical of metals has also not been observed. In contrast, the low-temperature behaviour of 'metallic' polymers has, in all previous cases, exhibited an increase in resistivity as temperature is further decreased, as a result of disorder-induced localization of the charge carriers1, 2, 3, 4. This disorder-induced localization also changes the infrared response such that () deviates from the prediction of Drude theory5, 6, 7. Here we report classic metallic transport data obtained from truly metallic polymers. With polyaniline samples prepared using self-stabilized dispersion polymerization8, we find that for samples having room-temperature conductivities in excess of 1,000 S cm-1, the resistivity decreases monotonically as the temperature is lowered down to 5 K, and that the infrared spectra are characteristic of the conventional Drude model even at the lowest frequencies measured.
Department of Physics, Pusan National University, Busan 609-735, Korea
Center for Polymers and Organic Solids, University of California at Santa Barbara, Santa Barbara, California 93106-5090, USA
Department of Molecular Science and Technology, Ajou University, Suwon 442-749, Korea