Electrosyntheses and characterizations of novel electrochromic and fluorescent copolymers based on 2,2′-bithiophene and pyrene

Poly (2,2′-bithiophene-co-pyrene), a novel copolymer, is successfully achieved by electrochemical oxidation of the monomer mixtures of 2,2′-bithiophene (BT) and pyrene in acetonitrile (ACN) containing sodium perchlorate (NaClO4). FT-IR and 1H NMR characterizations support that the obtained copolymers contain both pyrene and BT units. A series of experiments are carried out to investigate the properties of the copolymers obtained from 0.2 M NaClO4/ACN with different monomer feed ratios. The electrochemical properties of the obtained copolymers are studied by cyclic voltammetry (CV). Compared with polypyrene, the copolymers perform reversible redox process. Elemental analyses results indicate that the ratio of BT/pyrene units in copolymers increases as the feed ratio of BT/pyrene increases. The obtained copolymers also present properties of tunable electrochromism, good thermal stability and smooth morphology. The UV–vis absorption peaks of the copolymers exhibit obvious red-shift. Fluorescence spectra studies reveal that the copolymer is a good green-light emitter.