Compared temperature dependence of the electrical conductivity of unoriented and streched polycetylenes doped with heavy alkali metals

Abstract

Classical unoriented (CH) x synthesized using the technique of Ito et al. and highly oriented polyacetylene (HOPA) obtained after a method similar to the that proposed by Akagi et al. were doped to saturation with heavy alkali metal in the vapour phase. RT electrical conductivities in HOPA-based materials are 10 times higher than the values measured from doped-unoriented compounds. The thermal dependence of σ in the range 4.2–290 K is strongly dependent on the nature of the polymer used. In unoriented materials, the conductivity obeys a fluctuation induced tunn eling model, as proposed by Sheng, in a large domain of temperatures. To the contrary, the tridimensional variable range hopping is perfectly applicable to heavily doped HOPA compounds.