Ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate [BMIM]PF₆ has been used as solvent and electrolyte for the preparation of poly(3-bromothiophene) (PBrT) films by galvanostat and cyclic voltammetry. The structure and morphology of PBrT films were characterized by the means of the FT-IR spectrum and the scanning electron microscopy (SEM). The thermal stability of PBrT films has been inves-tigated through thermogravimetry and differential thermal analysis (TG-DTA). The electrochemical and electrochromic properties of PBrT flims were examined with UV-Vis spectrum, chronoamperometry, and chronoabsorptometry. The results showed that the surface morphology of PBrT films prepared in ionic liquid was denser and smoother than those prepared in traditional organic solvent. The PBrT films exhibited outstanding redox reversibility, good charging/discharging capacitance, high electroactive performance and good thermal stability. Electrochromic properties of the PBrT films showed a good color contrast and rapid response time (0.5 s). Ionic liquids exhibited wide electrochemical potential window, high conductivity and recyclability. Therefore, they open a promising field for the electropolymerization and so on.

Key words: ionic liquid [BMIM]PF₆, poly(3-bromothiophene), electropolymerization, electrochromism