Electrodissolution of poly(2,5-di-(2-thienyl)-pyrrole) in organic and hydro-organic media

Oxidized poly(2,5-di-(2-thienyl)-pyrrole) (poly(SNS)) films on Pt were reduced in common organic solvents under chronopotentiometric conditions. Electrodissolution was observed during reduction, being followed by ultramicrogravimetry. Thin films give an overall electro-dissolution in 0.1 M LiClO4 + acetonitrile solutions. The ratio between charges consumed during polymer stripping and those spent for its electrogeneration was 0.22–0.28. Between 0.24 and 0.34 electrons per monomeric unit were found to be required to electrodissolve the polymer. The electroreduction of oxidized poly(SNS) was also studied in aqueous mixtures of DMF, acetonitrile, acetone or methanol, containing 0.1 M LiClO4. In the water-rich regions, a constant weight loss of about 20% was always found, corresponding to the percentage of perchlorate ions lost during the electroreduction process, as confirmed by elemental analysis. Insoluble fractions of reduced poly(SNS) obtained in hydro-organic media contained small oligomers, from the dimer to the octamer, as detected by mass spectrometry-fast atom bombarding (MS-FAB). Scanning electron microscopy (SEM) micrographs of deposits produced in a 0.1 M LiClO4 aqueous solution showed that reduced polymer films are spongy.