Thermoelectric power and conductivity of iodine-doped ‘‘new’’ polyacetylene

We report measurements of the thermoelectric power and conductivity of ‘‘new’’ polyacetylene doped with iodine. In highly doped samples in which the conductivity extrapolates to finite values at zero temperature, we observe a nonlinearity in the thermopower very similar to that characteristic of the electron–phonon effect in metallic diffusion thermopower. The size of this nonlinearity is unusually small in the most highly conducting samples, as expected when the intrinsic conductivity is very large. For samples with additional sp3 defects or lower doping levels, in which the conductivity follows variable-range hopping behavior, we also find evidence for a hopping contribution in the thermopower.