Electrochemical oxidation of thin films of sigma-kappa-conjugated thienylene-silanylene copolymers, with poly[(hexamethyltrisilanplene)quinque(2, 5-thienylene)] (TSST) as a representative, is investigated in acetonitrile solutions containing different electrolytes. It is found from fluorescence spectroelectrochemical, electrochemical quartz crystal microbalance and FT-IR measurements that Si-Si-Si sigma-bonding is weakened by electrochemical anion doping in pi-conjugated segments of the polymer, resulting in promotion of cleavage of the sigma-bonding in BF4- and PF6- solutions. Such a doping-enhanced cleavage of the Si-Si-Si bonding is relatively negligible in a ClO4- solution, suggesting some specific interaction between the Si atoms in the polymer chain and the F atoms in BF4- and PF6- anions. In a F- solution, on the other hand, the polymer film undergoes electrochemical fluorination and/or chemical dissolution. (C) 2000 Elsevier Science Ltd. All rights reserved.