Electrochemistry of conductive polymers XVII. Preparation and characterization of polythiophene in aqueous solutions

Polythiophene has been prepared in aqueous solutions by repeatedly cycling potentials between −0.25 ∼ 1.75 V vs. the Ag/AgCl, saturated KCl reference electrode. The polymer films thus prepared were denser and more stable than those prepared in nonaqueous solutions. The film could be doped both anodically and cathodically depending on the solution pH. The films were not destroyed even when they are anodized at +2.5 V in 0.2 M LiCl solution at pH 3.0 The polymer films have their maximum absorbances observed between 350 nm and 420 nm depending on the electrolytes used, indicating the band gaps, and therefore chain lengths, of the polymers could be significantly different in different electrolyte solutions. The impedance values of the polymer were affected strongly by the pH and applied potential.