In this study, 9-(4-nitrophenylsulfonyl)-9H-carbazole (NPhSCz) monomer was chemically synthesized. The monomer characterization was performed by Fourier transform infrared spectroscopy, 1H-NMR, and melting point analysis. Two different electropolymerizations of NPhSCz were studied on a gold microelectrode (Au electrode) and carbon fiber microelectrodes (CFMEs) in a 0.1M sodium perchlorate (NaClO4)/acetonitrile solution. The electropolymerization experiments were done from 1 to 4 mM. The characterizations of two different modified electrodes of poly[9-(4-nitrophenylsulfonyl)-9H-carbazole] [poly(NPhSCz)] were performed by various techniques, including cyclic voltammetry, scanning electron microscopyenergy-dispersive X-ray analysis, and electrochemical impedance spectroscopy (EIS). The effects of the initial monomer concentrations (1, 2, 3, and 4 mM) were examined by EIS. The capacitive behaviors of the modified electrodes were defined via Nyquist, Bode magnitude, Bode phase, and admittance plots. The variation of the low-frequency capacitance (CLF) and double-layer capacitance (Cdl) values are presented at different initial monomer concentrations. Poly(NPhSCz)/CFME was more capacitive (CLF = 6.66 F/cm2 and Cdl 28 mF) than the Au electrode (CLF = 6.53 F/cm2 and Cdl 20 mF). An equivalent circuit model of R[QR(CR)(RW)](CR), (R: Current, Q: Constant phase element, C: Double layer capacitance, W: Warburg impedance), was used to fit the theoretical and experimental data. (c) 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011