In-situ FT-IR studies on cyclic voltammetry of polythiophene

In-situ FT-IR spectra were taken during a cyclic voltammetric study of polythiophene in 1M LiClO₄ in propylene carbonate. The external reflection technique was used in the spectroscopic measurements. A broad band extending from 1500 cm^–1 to higher wave numbers appeared during oxidation of polythiophene with a potential scan from 2.8 V to 4.2 V. Bands due to doping of the polymer at 1330 and 1020 cm^–1 were also found to increase during the same potential scan. The appearance of spectral changes above 3.3 V supports the model of two types of doping processes occurring in the polymer. The observed changes almost disappeared during the reverse scan.