Investigations on electric properties of polymers—V: On the a.c. conductivity of polyphenylacetylenes

The electric conductivity of polyphenylacetylene with various physical and isomeric structures (cis-cisoidal, cis-transoidal and trans-cisoidal) was investigated over the frequency and temperature ranges of 10-10⁵ Hz and 273–347 K, respectively. The transient currents from polyphenylacetylene having cis-cisoidal structure were also studied at 293 K. It was found that a.c. conductivity of cis-cisoidal polymer can be explained in terms of a hopping mechanism. The type of mechanism (classical or quantum) depends both on frequency and temperature. At temperatures <284 K and high frequencies, the quantum mechanism (predominantly by single hops) is involved. As frequency decreases and temperature increases, there is a gradual passing to the classical mechanism (many multiple hops) and then to the Maxwell-Wagner conduction. The electric properties of cis-transoidal polymer are similar to those of trans-cisoidal one, but are different from those for the cis-cisoidal structure. The quantum hopping mechanism, almost entirely involving single hops, seems to predominate in these two polymers. Adsorption of oxygen decreases both conductivity and dielectric constant, as compared with those in nitrogen, only in the case of cis-cisoidal polymer.