Electrochemical Polymerization and Characterization of Poly(3-(4-fluorophenyl)thiophene) in Pure Ionic Liquids

The electrochemical oxidation of 3-(4-fluorophenyl) thiophene (FPT) at a platinum electrode in pure 1-ethyl-2,3-dimethylimidazolium bis ((trifluoromethyl)sulfonyl) amide, EDMITFSI, and 1,3-diethyl-5-methylimidazolium bis ((trifluoromethyl)sulfonyl) amide, DEMITFSI, yielded an electroactive polymer. This polymer (PFPT) was similar to that prepared from common nonaqueous media such as tetraethylammonium tetrafluoroborate/acetonitrile, but it was characterized by slower ion insertion kinetics. A rapid loss of electroactivity of the polymer was observed upon cycling in pure ionic liquid, and that was attributed to gradual deswelling of the polymer. X-ray photoelectron spectroscopy measurements demonstrated that the doping processes of PFPT when cycled in pure ionic liquid were similar to those occurring in acetonitrile-based electrolyte and involved the incorporation of the anions (TFSI - ) of the ionic liquid when the polymer was oxidized to the p-doped state. The expulsion of these anions and the incorporation of the ionic liquid cationic species were observed upon reduction of the polymer to the fully n-doped state.