Electrochemical preparation and properties of poly(3‐aryl‐2,5‐thienylene)s

Abstract

AbstractFilms of poly(3‐phenyl‐2,5‐thienylene) (1a), poly[3‐(4‐methoxyphenyl)‐2,5‐thienylene] (1b) and poly[3‐(4‐trifluoromethylphenyl)‐2,5‐thienylene] (1c) were electrochemically prepared. The conductivities of 1a, 1b and 1c were determined to be 140, 40, and 1,8 · 10−3 S/cm, respectively. The surfaces of 1a and 1b are considerably rough. The infrared spectra of electrochemically neutralized polymers showed that they have a regular structure. Cyclic voltammograms showed that the oxidation potential increases in the order 1b < 1a < 1c (in the neutral state). The results are discussed in terms of the electronic effect of the substituents. The visible spectra of these neutral polymers showed that the π‐π*‐transition occurs at lower energy than that of poly(2,5‐thienylene) (1d). This indicates that the pendant aryl groups are conjugated with the main chain. The effect of substituents on the peak positions of the π‐π* transition is hardly discernible. 1a is highly anode‐active as compared with 1d. The spectral change of 1a upon PF doping presumably is the indication of polarons at low doping levels. The changes during Et4N+ doping shows that cation doping took place.