The dc conductivity of polyphenylacetylene below room temperature

Abstract
The temperature dependence of the dc conductivity for doped and undoped cis-polyphenylacetylene (PPA) is analyzed at temperatures of 110 to 300 K. The dc conductivity (σdc) data of arsenic pentafluoride-doped and iodine-doped samples suggest two major current conduction processes separated by a characteristic temperature (Tc) of about 257 K, which is independent of the doping level. At TTc, σdc is activated with an activation energy that, for PPA-AsF5, varies from 0.86 eV to 0.51 eV for doping levels of 2×10−3 to 7×10−2 moles dopant/moles monomer, respectively. PPA annealed at 130 °C, which is known to undergo isomerization and cyclization reactions, has a Tc of about 210 K, and σdc does not respond to doping. Possible conduction mechanisms are discussed.

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