ELECTROCHEMICAL OXIDATION OF 2,5-DI-(-2-THIENYL)-PYRROLE IN ACETONITRILE - CATHODIC STRIPPING OF THE ELECTROGENERATED CONDUCTING POLYMER

The electrochemical behaviour of 2,5-di-(-2-thienyl)-pyrrole was studied by cyclic voltammetry, chronoamperometry and chronopotentiometry. The monomer oxidation-polymerization takes place on platinum at potentials more positive than 0.3 V vs SCE. At higher potentials, the oxidation processes in the polymer layer seem to control the generation of the polymer and the polymer properties. Polymer films electrogenerated at potentials lower than 0.7 V are insoluble in LiClO4 + acetonitrile solutions. When the polymer film is reduced electrochemically, it becomes soluble. The solubility is a faradaic process: the weight of electrochemically solubilized polymer is proportional to the cathodic electrical charge consumed. The linearity of the process was proved using different cathodic current densities. The polymer oxidation at potentials more positive than 1 V promotes the insolubility of the polymer, probably by a crosslinking process. The reduction of the polymer at potentials below 0.2 V promotes stripping of the polymer from the electrode. The polymer structure was studied by Fourier transform IR reflectance. The UV-Vis study of the oxidized and reduced polymer in solution led to the band structure and showed the self-reduction of the dissolved polymer.