Investigation of polycarbazoles thin films prepared by electrochemical oxidation of 3- and 9-substituted carbazoles

Conducting polymers such as polycarbazole and its derivatives have attracted much attention due to their remarkable electrical and optical properties. To prepare polycarbazole derivatives, a variety of substituents can be added to the nitrogen atom of the carbazole monomers or to their 3- and 6-positions. In the present study, carbazole monomers bearing hydrogen, methyl or benzyl group at the N-position and styryl or (naphthalen-1- or -2-yl)vinyl substituents at the 3-position were synthesized. Then, the electro-oxidation of the different carbazole derivatives was carried out in acetonitrile with potentiodynamic and potentiostatic electrochemical methods. Although all monomers were successfully electrochemically oxidized, leading to the formation of polymer films on the working electrode surface, the electrochemical behavior, electrochromic properties, morphology, thickness, and roughness of the films varied greatly depending on the nature of the substituents. Among all the polycarbazole films obtained, those prepared from monomers unsubstituted at 9-position appeared to be the most promising due to their high electroactivity, electrochromism, good adhesion to the substrate and homogeneous structure.