Controlled electrocopolymerization of thiophene with N-ethyl carbazole: In-situ and EX-situ spectroelectrochemical investigation and conductivity relationship

Polymerization of thiophene (Th) was studied in the presence of N-ethyl carbazole (ECz) by in-situ and ex-situ spectroelectrochemical measurements. In-situ spectroelectrochemical measurements allow determining some soluble thiophene oligomers. Cooligomeric species of Th-ECz (which give peaks at 376, 400 nm) are in parallel line with the findings from CV measurements (current values of peaks of electrogrowth of polymer). Results also suggest that ethylcarbazole and thiophene react on the electrode surface as well as in solution, and the percentage of ECz incorporated into the polymer structure is less than in the case of the electrode surface reaction. CV's of PECz, PTh and P [Th-co-ECz] formation indicate shifts in E_p and corresponding current changes. Increase in peak currents intensities of ECz in the presence of Th, I_p1 for ECz, Th, [Th-co-ECz] is 0.05 mA, 1.6 mA, 2.0 mA, respectively, giving a ratio of 1/32/40 (I_p1) and 1/9/21 (I _p2) supporting the inclusion of ECz into copolymer structure. The conductivities of PTh and copolymer-measured by four-point-probe technique (at mole ratio of n_Th/n_Ecz=25) were found as 42 mS/cm and 36 mS/cm, respectively, giving a ratio of 42/36 = 1.67, which is in line with I_p values of electro growth of copolymer on the Pt [i.e., for ratios of P[Th-co-Ecz]/PTh of I_p1, 40/32 = 1.3 and for I_p2=21/9 =2.3].