ELECTROCHEMICAL DEPOSITION OF POLY(O-ANISIDINE) AND POLYPYRROLE AT OCTADECANETHIOL COATED GOLD ELECTRODES

The o-anisidine and pyrrole have been polymerized by the electrochemic al oxidation of monomers on gold electrodes, covered with self-assembl ed monolayers. The obtained polymer-monolayer systems have been invest igated by cyclic voltammetry in aqueous supporting electrolyte solutio ns containing K4Fe(CN)(6) and RU(NH3)(6)Cl-3 The deposition of conduct ing polymers strongly depends on the integrity of a monolayer. In the case of a large number of SAM defects, the polymerization of o-anisidi ne and pyrrole leads to the formation of nuclei of the conducting poly mer in the insulating matrix of the thiol monolayer. When the polymer is in the conducting (oxidized) form, the nuclei act as an array of mi croelectrodes. The polarogram-shaped voltammograms obtained for K4Fe(C N)(6) confirm the hemispherical diffusion of redox species to the poly mer nuclei. When the polymer is in the non-conducting (reduced) form, the polymer-octadecanethiol layer blocks the redox processes on the el ectrode. The exponential-type CV curves observed for Ru(NH3)(6)Cl-3, w hen the polymer is in its non-conducting state, can be assigned to the tunnelling of electrons through the passivating layer. The use of mon olayers with a low number of defects influences the mechanism of polym er growth. Thus, the polypyrrole grows on the layer of thiols, and the poly(o-anisidine) forms polymer nuclei. (C) 1998 Elsevier Science S.A . All rights reserved.