INFLUENCE OF CHAIN-LENGTH AND DEFECTS ON THE ELECTRICAL-CONDUCTIVITY OF CONDUCTING POLYMERS

In-situ conductivity measurements were carried out on a defined conjugated oligomer and the corresponding conducting polymer, i.e. p-sexiphenylene and polyphenylene respectively. At low doping levels the conductivity of the oligomer is better than that of the polymer. By contrast, at high doping levels the situation is inverse. This may be explained in terms of two different conductivity mechanisms, hopping between chains and chain conductivity respectively. For the first time, the influence of chain length and the number of defects on the overall electrical conductivity was studied quantitatively during solid state electropolymerization of p-sexiphenylene. The conductivity of the polymer with the longest experimentally accessible chains exceeded that of p-sexiphenylene by about two orders of magnitude. Cross-linking of these chains lead to a dramatic decrease of the conductivity.