Copolymers of carbazoles and methyl ethyl ketone formaldehyde resin

Purpose - The purpose of this paper is to develop the soluble and processable conducting copolymers of carbazole (Cz), ethylcarbazole (ECz), N-vinylcarbazole (NVCz) by oxidatively polymerising carbazoles by ceric ammonium nitrate (CAN) in the presence of methyl ethyl ketone formaldehyde resin (MEKF-R); and to report the advantages of obtaining copolymer structure. Design/methodology/approach - A new class of soluble and conductive P(Cz/MEKF-R), P(NVCz/MEKF-R) and P(ECz/MEKF-R) copolymers were synthesised by the method of oxidative polymerisation with ceric ammonium nitrate. MEKF-R, CAN and carbazole monomers (Cz, NVCz and ECz) were dissolved in acetonitrile separately. Then, the CAN solution was added dropwise into the mixture of MEKF-R and Cz, NVCz or ECz solutions while stirring and a green powder was formed almost instantaneously. After one hour stirring at 25°C, the powder was filtered, washed with acetonitrile and dried at room temperature. A green coloured product was obtained. The colourless insulator copolymer present in this product was separated by selectively dissolving with toluene. The insoluble green copolymer was filtered off and dried at room temperature under vacuum. The products were characterised by FTIR, DSC thermograms, 1H-NMR, four-point probe conductivity and atomic absorption measurements. Findings - The solubility and conductivity of the Cz/MEKF-R copolymer P(Cz/MEKF-R), the NVCz/MEKF-R copolymer P(NVCz/MEKF-R) and the ECz/ MEKF-R copolymer P(ECz/MEKF-R) were regulated by the ratios of (Cz, NVCz, ECz)/CAN/MEKF-R. By inclusion of the ketonic resin segments to the polycarbazole chains, thermally processable copolymers have been obtained with a melting point of about 80°C. FT-IR results in different reaction time and the presence of metal in copolymers show together a complex between monomer-metal and resin. Research limitations/implications - This study focuses on obtaining conductive, soluble and processable copolymers. Since the ketonic resin is an insulator, in order to obtain both conductive and totally soluble polymer, successively regulating the ratios of (Cz, NVCz, ECz)/CAN/MEKF-R is necessary. Practical implications - This work provides technical information for the synthesis of conducting and totally soluble copolymer. Originality/value - The conductive P(Cz/MEKF-R), P(NVCz/MEKF-R) and P(ECz/MEKF-R) copolymers obtained by the method of oxidative polymerisation with ceric ammonium nitrate, which are totally soluble in DMF, could only be produced with this method and may increase the area of application of the carbazole polymers.