EQCM and in situ conductance studies on the polymerisation and redox features of thiophene co-polymers

3-Thiophene-acetic acid and 3-methylthiophene co-polymers have been prepare d with the consideration that the solvation behaviour of the film could be modified. The modification is coupled with the observed splitting of the ox idation peak on the cyclic voltammograms. The redox transformation of the f ilms was studied by electrochemical quartz crystal microbalance (EQCM) and in situ conductance (ISC) techniques. Mass changes during the electrochemic al processes showed that the cation is not involved into the charge balanci ng of the film. Manifestation of self-doping was excluded by analogous meas urements with an aprotic co-polymer of methylthiophene. Results completed w ith in situ conductance and spectroelectrochemical observations confirmed t he assumption of a chemical step taking place after the first oxidation. In this process desolvation of the oxidised intermediate occurs, which is a n ecessary step for the achievement of the quasi-metallic state. (C) 2000 Els evier Science Ltd. All rights reserved.