Anodic polymerization of α-tetrathiophene in organic medium. Doping with perchlorate ion and properties of conducting polymer (original) (raw)

2002, Electrochimica Acta

The electrochemical behavior of a-tetrathiophene (a-TTF) on Pt has been studied from concentrated monomer solutions in acetonitrile or mixtures of acetonitrile/nitrobenzene/DMF with 0.1 M LiClO 4 . For a 1.0 mM a-TTF solution in 50:30:20 acetonitrile/nitrobenzene/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(a-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 ClO 4 − counterions, and contain a number of ionic couples of Li + ClO 4 − 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 a-TTF into the polymer, points to the formation of crosslinked chains. This is consistent with the predominance of b -b linkages into the polymer, as confirmed by IR spectroscopy. Poly(a-TTF) doped with ClO 4 − ions has a very low conductivity, which is ascribed to the low number of polarons present in its monomeric units.

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