Fluorescent and electrochromic polymers from 2,8-di(carbazol-9-yl)dibenzothiophene and its S,S-dioxide derivative

• 2,8-Di(carbazol-9-yl)dibenzothiophene and its S,S-dioxide derivative were synthesized.
• Polymers were synthesized by chemical and electrochemical oxidative polymerization.
• Fluorescence and solvatochromism of the monomers and polymers were studied.
• The polymers displayed multi-colored electrochromic behavior.

We report the synthesis and characterization of two carbazole-endcapped monomers, namely 2,8-di(carbazol-9-yl)dibenzothiophene (SCz) and 2,8-di(carbazol-9-yl)dibenzothiophene S,S-dioxide (SO2Cz), and their derived polymers PSCz and PSO2Cz prepared by both FeCl3 oxidative coupling and electropolymerization processes. The dilute solutions of PSCz and PSO2Cz prepared by chemical oxidative coupling exhibited fluorescent and solvatochromic behavior. Thin polymeric films could be robustly electrodeposited onto the surface of the ITO-glass substrate by repetitive cyclic voltammetry scanning of monomers SCz and SO2Cz in an electrolyte solution between 0 and 1.8 V. The electrochemically generated polymer films exhibited two reversible oxidation redox couples due to successive oxidations of the biscarbazole unit. These polymer films also revealed good electrochemical and electrochromic stability, with coloration change from a colorless neutral state to yellow, green and blue oxidized states. Switching ability of the polymers was evaluated by kinetic studies upon measuring the percent transmittance (%T) at their maximum contrast point, indicating that the polymers exhibit moderate electrochromic performance.

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