2,7-Linked N-methylcarbazole copolymers by combining the macromonomer approach and the oxidative electrochemical polymerization

Abstract

The preparation of copolymers bearing N-methylcarbazole and 2,7-linked 3,4-ethylenedioxythiophene units has been carried out using the N-methyl-2,7-di(2-(3,4-ethylenedioxythienyl))carbazole monomer, which has been chemically synthesized through the Stille coupling reaction of 2,7-dibromo-N-methylcarbazole and tributyl-stannylated 3,4-ethylenedioxythiophene. Then, the monomer was electropolymerized by chronoamperometry in acetonitrile with 0.1 M LiClO4 under a constant potential of 0.70 V and using steel AISI 316 electrodes. The electrochemical activity and stability, charge–discharge capacity, charge transfer resistance and surface properties (i.e. morphology, topography and wettability) of the resulting polymer have been characterized and compared with those reported for poly(3,4-ethylenedioxythiophene). Finally, the polymer has been obtained by potentiodynamic sweep, applying around 100 cyclic voltammetry steps to an acetonitrile solution of the N-methyl-2,7-di(2-(3,4-ethylenedioxythienyl))carbazole monomer with 0.1 M LiClO4. Results show that although this technique has been mostly used to electropolymerize diheteroaromatic-subtituted carbazoles, the resulting material presents serious disadvantages with respect to that produced by chronoamperometry under a constant potential.