Anodic polymerization of α-tetrathiophene in organic medium.: Doping with perchlorate ion and properties of conducting polymer

The electrochemical behavior of alpha-tetrathiophene (alpha-TTF) on Pt has been studied from concentrated monomer solutions in acetonitrile or mixtures of acetonitrile/nitrobenzene/DMF with 0.1 M LiClO4. For a 1.0 mM alpha-TTF solution in 50:30:20 acetonitrile/nitrobenzone/DMF, three consecutive oxidation peaks are detected by cyclic voltammetry (CV), In this medium, uniform, insoluble, adherent and black polymeric films are obtained by chronopotentiometry (CP) until 0.5 mA cm(-2) and by chronoamperometry (CA) from 0.900 to 1.200 V versus Ag\AgCl, corresponding to the first oxidation stage. Control voltammograms of films synthesized from 1.000 to 1.100 V show a redox pair related to electroactive polarons formed during poly(alpha-TTF) generation, followed by a reduction peak associated with bipolaronic states. Elemental analysis of polymers allows to determine that their monomeric units always support approximately 0.31 positive charges, balanced with ClO4- counterions. 4 and contain a number of ionic couples of Li+ ClO4 ranging between 0.01 and. 0.06. These results, along with the low productivity and high number of electrons required to incorporate one molecule of alpha-TTF into the polymer, points to the formation of crosslinked chains. This is consistent with the predominance of beta-beta linkages into the polymer, as confirmed by IR spectroscopy. Poly(alpha-TTF) doped with ClO4- ions has a very low conductivity, which is ascribed to the low number of polarons present ill its monomeric units. (C) 2002 Elsevier Science Ltd. All rights reserved.