Polyphenylenes were prepared by using biphenyl-AICl3-CuC1, according to cationic oxidative polymerization. The chlorobenzene soluble fraction was doped with 10 O/o (w/v) solution of FeCI, in acetonitrile. The alternating electrical conductivity, X-ray diffractograms and the FTIR-spectra of both undoped and doped polyphenylenes were measured. The proportion of the components used for the preparation of polyphenylenes strongly influences their structure as well as their conductive properties. The undoped polyphenylenes were found to be insulators, but most of them became semiconductors after doping. The increase of the alternating electrical conductivity u' (resulting from the real part of the admittancevector) of the doped polyphenylenes has been explained considering the factors that influence the polyphenylenes structure: the high ratio of paralmeta, the presence of both amorphous and crystalline regions, and the presence of polynuclear structures. On the other hand, the presence of aliphatic structures interrupts the conjugation system, leading to lower u' values.

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