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

In-situ conductivity measurements were carried out on a defined conjug ated oligomer and the corresponding conducting polymer, i.e. p-sexiphe nylene and polyphenylene respectively. At low doping levels the conduc tivity of the oligomer is better than that of the polymer. By contrast , at high doping levels the situation is inverse. This may be explaine d in terms of two different conductivity mechanisms, hopping between c hains and chain conductivity respectively. For the first time, the inf luence of chain length and the number of defects on the overall electr ical conductivity was studied quantitatively during solid state electr opolymerization of p-sexiphenylene. The conductivity of the polymer wi th the longest experimentally accessible chains exceeded that of p-sex iphenylene by about two orders of magnitude. Cross-linking of these ch ains lead to a dramatic decrease of the conductivity.