Electrogeneration of conducting poly(α-tetrathiophene). Effect of solution stirring and detection of linear oligomers

The anodic oxidation of α-tetrathiophene on Pt was studied in a 1.0 mM monomer solution in 0.1 M LiClO 4 in 45:35:20 acetonitrile/ethanol/DMF. Three consecutive oxidation peaks were detected by cyclic voltammetry, along with a cathodic peak related to the reduction of electroactive polarons formed during the first anodic process. Uniform, adherent, insoluble and black polymer films were obtained by chronoamperometry at 1.000 V vs Ag|AgCl corresponding to the first oxidation-polymerization process. Stirring of monomer solution promotes the production of polymer, favoring the oxidation of polymer chains with the incorporation of more doping ClO 4 - ions and ion pairs of Li + ClO 4 - in their monomeric units. The conductivity of the polymer obtained under stirring was three orders of magnitude higher than that synthesized from a quiescent solution. The scanning electron microscopy images also showed much more uniform films under stirring. This behavior points to the existence of less crosslinking in the polymer and the production of longer linear chains when the solution is stirred. IR analysis of these materials confirmed the formation of crosslinked chains with predominance of β-β linkages. Short linear oligomers such as the dimer, trimer and tetramer were detected in all polymers by MALDI-TOF-MS, thus showing a radical polycondensation as initial electropolymerization mechanism. A larger proportion of linear oligomers is formed under solution stirring.

[1]  W. Plieth,et al.  Synthesis and characterization of thiophene/3-alkylthiophene random cooligomers , 2002 .

[2]  F. Estrany,et al.  Anodic polymerization of α-tetrathiophene in organic medium. Doping with perchlorate ion and properties of conducting polymer , 2002 .

[3]  K. Kaeriyama,et al.  Preparation and properties of polythiophene derivatives , 2001 .

[4]  F. Estrany,et al.  Electropolymerization of 2,5-di-(-2-thienyl)-pyrrole in ethanolic medium. Effect of solution stirring on doping with perchlorate and chloride ions , 2000 .

[5]  P. Audebert,et al.  Redox chemistry of thiophene, pyrrole and thiophene-pyrrole-thiophene oligomers , 1999 .

[6]  B. Divisia-Blohorn,et al.  Electropolymerization mechanism of poly(dibenzylidene)tetrathiapentalene , 1999 .

[7]  David M. Collard,et al.  Chemical and Electrochemical Polymerization of 3-Alkylthiophenes on Self-assembled Monolayers of Oligothiophene-Substituted Alkylsilanes , 1999 .

[8]  E. Brillas,et al.  Electrogeneration of conducting poly(2,5-di-(-2-thienyl)-furan) , 1998 .

[9]  A. Guyard,et al.  REDOX CHEMISTRY OF BIPYRROLES : FURTHER INSIGHTS INTO THE OXIDATIVE POLYMERIZATION MECHANISM OF PYRROLE AND OLIGOPYRROLES , 1997 .

[10]  J. Garrido,et al.  Faradaic impedance behaviour of oxidized and reduced poly (2,5-di-(2-thienyl)-thiophene) films , 1997 .

[11]  E. Brillas,et al.  Electrogeneration and solubilities of oxidized poly(2,5-di-(-2-thienyl) -thiophene) , 1996 .

[12]  J. Heinze,et al.  Electrochemical solution and solid-state investigations on conjugated oligomers and polymers of the α-thiophene and the p-phenylene series , 1996 .

[13]  E. Salatelli,et al.  Properties of a hydroxydecyl‐functionalized polythiophene synthesized by the iron trichloride route , 1995 .

[14]  F. Urpí,et al.  Oxidized and reduced poly(2,5-di-(-2-thienyl)-pyrrole): solubilities, electrodissolution and molar mass , 1995 .

[15]  A. Yassar,et al.  All-Polymer Field-Effect Transistor Realized by Printing Techniques , 1994, Science.

[16]  Toribio F. Otero,et al.  Parallel kinetic studies of the electrogeneration of conducting polymers: mixed materials, composition and properties control , 1994 .

[17]  J. Pernaut,et al.  Electrochemical reactivity of the oxidized species of thiophene oligomers. Formal oxidation potential of α-bromo-α′-methoxy-quaterthienyl , 1993 .

[18]  L. Overgaard,et al.  Reactivity of 2,5-dithienyl-pyrroles and thiophenes , 1993 .

[19]  R. T. Carlin,et al.  A mechanistic study of the electrochemical oxidation of 2,5-bis(2-thienyl)pyrroles , 1993 .

[20]  J. Pernaut,et al.  Effect of end substitution on electrochemical and optical properties of oligothiophenes , 1993 .

[21]  J. Tour,et al.  Chain-length dependence of electrochemical and electronic properties of neutral and oxidized soluble .alpha.,.alpha.-coupled thiophene oligomers , 1992 .

[22]  D. Fichou,et al.  Electrochemical synthesis of alpha-conjugated octi- and decithienyl oligomers , 1989 .

[23]  J. Ferraris,et al.  Optical, electrical and electrochemical properties of heteroaromatic copolymers , 1989 .

[24]  A. Galal,et al.  The Spectroelectrochemical Determination of “Formal Potentials and n‐Values” of Some Electrochemically Formed Conducting Poly(heterolene) Films , 1988 .

[25]  H. Zimmer,et al.  Steric Effects on the Controlled Potential Electro‐Oxidation of 3‐Methylthiophene and Thiophene Oligomers and the Properties of their Polymer Films , 1988 .

[26]  J. Roncali,et al.  Poly mono-, bi- and trithiophene: effect of oligomer chain length on the polymer properties , 1986 .

[27]  G. Bidan,et al.  Spectroelectrochemical study of polypyrrole films , 1983 .

[28]  F. Estrany,et al.  Effects of Doping on the Electrochemical and Electrical Properties of Poly(2,5-di(2-thienyl)pyrrole) , 1999 .

[29]  Marco-A. De Paoli,et al.  A solid state artificial muscle based on polypyrrole and a solid polymeric electrolyte working in air , 1997 .