Oxidative polymerization of acrylonitrile (AN) initiated by Ce(IV)-oxalic acid redox system in the aqueous medium was performed and polyacrylonitrile (PAN)/polypyrrole (PPy) composite thin films were prepared by polymerization of pyrrole on polyacrylonitrile matrix. Effect of concentration of pyrrole derivatives on the resulting polymeric film properties was investigated. The influence of the pyrrole derivative type and content on the dielectric permittivity, dielectric loss and electrical properties of the composite films were analyzed in the frequency range from 0.05 Hz to 10 MHz. For a selected concentration of 200 mu l of composite films at 10(7) Hz. the conductivity was found to be in the following order: PAN-PPy < PAN-PNMPy < PAN-PNPhPy. Dielectric constant increase of the composite films was more obvious when the quantity of n-phenyl pyrrole was increased. A linear relationship was observed between the absorbances (FTIR-ATR) and conductivities (dielectric spectroscopy). (C) 2010 Elsevier B.V. All rights reserved.