Electrodeposition of High-quality Polycarbazole Films in Composite Electrolytes of Boron Trifluoride Diethyl Etherate and Ethyl Ether

High-quality polycarbazole (PCZ) films were synthesized electrochemically by direct oxidation of carbazole in boron trifluoride diethyl etherate (BFEE) containing vol. 20% ethyl ether (EE). The oxidation potential of carbazole in this medium was measured to be only 0.90 V vs. SCE, which was lower than that determined in acetonitrile containing 0.1 mol l⁻¹ Bu₄NBF₄ (1.35 V vs. SCE). PCZ films obtained from this medium showed better electrochemical behavior, better thermal stability with conductivity of 7.5 × 10⁻³ S cm⁻¹ being one order of magnitude higher than those reported previously, indicating that BFEE/EE was a better medium than acetonitrile for the electrosyntheses of PCZ films. As-formed PCZ films can be partly dissolved in acetone, acetonitrile and tetrahydrofuran. Spectral analysis provided evidence for the existence of the conjugated structure of the PCZ chain. Fluorescent spectra indicate that electrosynthesized PCZ is an ideal blue light emitter.