Electrochemical Polymerization of Carbazole in Acetic Acid Containing Boron Trifluoride Diethyl Etherate

High-quality polycarbazole (PCz) films with an electrical conductivity of 10(-2) S.cm(-1) were synthesized electrochemically by direct anodic oxidation of carbazole in a novel mixed electrolyte of acetic acid containing 26% boron trifluoride diethyl etherate (BTDE) and 5% poly(ethylene glycol) with molar mass of 400 (by volume). The oxidation potential of carbazole in this medium was measured to be only 0.89 V vs. a saturated calomel electrode (SCE), which was much lower than that determined in acetonitrile containing 0.1 mol.L-1 Bu4NBF4 (1.36 V vs. SCE). PCz films obtained from this medium showed good electrochemical behavior, good thermal stability, and were partly soluble in strong polar organic solvents such as dimethyl sulfoxide and tetrahydrofuran. The fluorescence spectra implied that PCz obtained from this medium was a good blue-light emitter. FT-IR, H-1 NMR and theoretical studies showed that the polymerization of carbazole mainly occurred at the 3,6-positions. To the best of our knowledge, this is the first report on the electrosyntheses of conducting polymers in mixed electrolyte of acetic acid and BTDE.