Electrochemical preparation and characterization of a new conducting copolymer of 2,7-carbazole and 3-octylthiophene

In the present work, the synthesis and study of the electrochemical behavior of 2,7-bis(3-octylthiophene-2-yl)-N-methylcarbazole are reported. The electropolymerization of this monomer was achieved by potentiodynamic cyclic voltammetry and potentiostatic techniques. Voltammograms show that two different conducting deposits are formed on Pt for oxidation at 1.0 and 0.8 V. The nature of the deposits depends on the applied potential and the scan rate. Both deposits exhibit n- and p-doping/undoping processes that are thermodynamically reversible and kinetically partially reversible. The same behavior was determined on fluorine-doped tin oxide. The nucleation and growth mechanism (NGM) of the electropolymerization were investigated using a potentiostatic technique (i–t). Two mechanisms were obtained, and the deconvolution of the current–time transient for the low-potential data fitted with a theoretical model suggesting that at short times, an instantaneous nucleation with a two-dimensional growth contribution prevails, followed by a three-dimensional progressive nucleation with a transfer charge diffusion. Finally, at longer times, a three-dimensional progressive nucleation with a diffusion-controlled growth contribution becomes important. The morphology predicted from these NGMs fully correlates with that determined by scanning electron microscopy.