In this paper, we have investigated the electrochemical behavior of a soluble copolymer of poly(aniline) (PANI) and poly(phenylene sulfide) in organic media. By using 'in situ' UV-vis and Raman spectroscopies, it was proved that during the oxidation of the first cycle, polarons and bipolarons are formed consecutively, due to the loss of electrons from the nitrogen and sulfur, respectively. In addition, it was verified that the formation of polarons is reversible while the formation of bipolarons is irreversible. In the second and subsequent cycles, only one reversible redox process is observed. This process corresponds to the transformation of polarons to bipolarons and vice versa. The 'in situ' resistance measurements have indicated that bipolarons are the charge carriers for doped PPSA, distinctly than it was observed for PANI. (c) 2005 Elsevier Ltd. All rights reserved.