Anomalous thermal conductivity of polyacetylene

Measurements of the specific heat and of the thermal conductivity of pure and iodine doped polyacetylene from liquid helium to room temperature are reported. The thermal conductivity rises linearly from 3 to 50 K and with about the third power of the temperature from 50 to 300 K. The kink at 50 K corresponds to a very unusual minimum of the phonon mean free path, probably caused by resonant scattering of fast thermal phonons (which travel along the chains) on low frequency interchain modes. These results suggest that the polymer chains are oriented parallel to the well-known fibers in polyacetylene.