Effects of doping on the electrochemical and electrical properties of poly(2,5-di(2-thienyl)pyrrole)

The electropolymerization of 2,5-di(2-(thienyl)pyrrole) (SNS) on a Pt elect rode from ethanolic solution with LiClO4 or LiCl as electrolyte has been st udied 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 charg es formed in both oxidized polymers are compensated by the entrance of anio ns from solution. Elemental analysis reveals that polymers generated at a l ow oxidation potential by CA contain a 21.03% (w/w) of ClO4- or a 9.56% (wi w) of Cl-. The poly(SNS) doped with Cl- presents higher proportion of reduc ible positive charges, higher polymerization charge and lower productivity. A much higher electrical conductivity, however, has been found for the pol y(SNS) doped with ClO4-. Both polymers are soluble in DMSO, acetone and met hanol. The dimer, trimer, tetramer and pentamer have been detected as solub le 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 alpha-alpha linkages between monomeric units. A condensation mechanism involving one-electron oxidation of all ele ctrogenerated linear and neutral polymeric chains is proposed to explain th e SNS electropolymerization.