Collect. Czech. Chem. Commun. 1999, 64, 1357-1368

Effects of Doping on the Electrochemical and Electrical Properties of Poly(2,5-di(2-thienyl)pyrrole)

Enric Brillasa, José Carrascob, Ramon Oliverc,*, Francesc Estranyc and Víctor Ruizc

a Laboratori de Ciència i Tecnologia Electroquímica de Materials, Departament de Química Física, Facultat de Química, Universitat de Barcelona, Martí i Franqués 1, 08028 Barcelona, Spain
b Departament d'Enginyeria Química i Metallúrgia, Facultat de Química, Universitat de Barcelona, Martí i Franqués 1, 08028 Barcelona, Spain
c Departament d'Enginyeria Química, Escola Universitària d'Enginyeria Tècnica Industrial de Barcelona, Universitat Politècnica de Catalunya, Comte d'Urgell 187, 08036 Barcelona, Spain


The electropolymerization of 2,5-di(2-(thienyl)pyrrole) (SNS) on a Pt electrode from ethanolic solution with LiClO4 or LiCl as electrolyte has been studied by cyclic voltammetry (CV) and chronoamperometry (CA). In both media, a quasi-reversible process has been indicated by CV, reversing the scan at low oxidation potentials. Under these conditions, reducible positive charges formed in both oxidized polymers are compensated by the entrance of anions from solution. Elemental analysis reveals that polymers generated at a low oxidation potential by CA contain a 21.03% (w/w) of ClO4- or a 9.56% (w/w) of Cl-. The poly(SNS) doped with Cl- presents higher proportion of reducible positive charges, higher polymerization charge and lower productivity. A much higher electrical conductivity, however, has been found for the poly(SNS) doped with ClO4-. Both polymers are soluble in DMSO, acetone and methanol. The dimer, trimer, tetramer and pentamer have been detected as soluble and neutral linear oligomers by mass spectrometry-fast atom bombardment. The analysis of polymers by infrared spectroscopy confirms the predominant formation of linear molecules with α-α linkages between monomeric units. A condensation mechanism involving one-electron oxidation of all electrogenerated linear and neutral polymeric chains is proposed to explain the SNS electropolymerization.

Keywords: 2,5-Di(2-thienyl)pyrrole; Electropolymerization; Cyclic voltammetry; Oligomers; Chronoamperometry; Conductivity; Pyrroles; Thiophenes.