Synthesis of 9-(4-nitrophenylsulfonyl)-9H-Carbazole: Comparison of an Impedance Study of Poly[9-(4- nitrophenylsulfonyl)-9H-carbazole] on Gold and Carbon Fiber Microelectrodes Murat Ates, Nesimi Uludag Department of Chemistry, Faculty of Arts and Sciences, Namik Kemal University, Degirmenalti Campus, 59030 Tekirdag, Turkey Received 27 May 2011; accepted 27 July 2011 DOI 10.1002/app.35380 Published online 6 December 2011 in Wiley Online Library (wileyonlinelibrary.com). ABSTRACT: In this study, 9-(4-nitrophenylsulfonyl)-9H- carbazole (NPhSCz) monomer was chemically synthesized. The monomer characterization was performed by Fourier transform infrared spectroscopy, 1 H-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 per- chlorate (NaClO 4 )/acetonitrile solution. The electropolymeri- zation 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 vol- tammetry, scanning electron microscopy–energy-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 mag- nitude, Bode phase, and admittance plots. The variation of the low-frequency capacitance (C LF ) and double-layer capacitance (C dl ) values are presented at different initial monomer concen- trations. Poly(NPhSCz)/CFME was more capacitive (C LF ¼ 6.66 F/cm 2 and C dl  28 mF) than the Au electrode (C LF ¼ 6.53 F/cm 2 and C dl  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. V C 2011 Wiley Periodicals, Inc. J Appl Polym Sci 124: 4655–4662, 2012 Key words: coatings; fibers; redox polymers; synthesis; thin films INTRODUCTION Conducting polymers (CPs) have been a subject of intense investigation by many research groups worldwide. During the past decade, there have been many articles related to CPs; these have led to prac- tical applications in various areas, such as batteries, sensors, antistatic coatings, and supercapacitors. 1–3 Electrochemical impedance spectroscopy (EIS) 4,5 has been used to study the electrical properties of thin films of electroactive CPs. 6 The functional groups in the modified polymers open the possibility of using such electrocoated polymers serving as electrochemi- cal capacitors. 7–9 In previous studies, the electropoly- merization of carbazole derivatives was examined with various functional groups, such as the anionic polymerization of 4-(9-carbazolyl) methyl styrene, 10 poly(N-alkyl-3,6-carbazoles), 11 poly[9-(4-vinylbenzyl)- 9H-carbazole], 12 poly(N-hydroxyl methyl carbazole), 13 poly(N-vinyl carbazole), 14 poly(9-tosyl-9H-carbazole- co-pyrrole), 15 5-(3,6-dibromo-9H-carbazole-9-yl) pen- tane nitrile, 16 poly(9-benzyl-9H-carbazole), 17 and poly(9-tosyl-9H-carbazole). 18 Carbon fibers have present extremely high strength and modulus values, good stiffness, creep resistance, and so on. 19 The application of a poly- meric interface acting as a coupling agent can improve the interfacial properties between reinforc- ing carbon fiber microelectrodes (CFMEs) and the polymeric matrix. 20 The surfaces of coated CFMEs have been characterized by electrochemical charac- terization techniques. 21–24 In this article, the synthesis of 9-(4-nitrophenylsul- fonyl)-9H-carbazole (NPhSCz) and its characterization were presented by Fourier transform infrared (FTIR) spectroscopy, 1 H-NMR, and melting point analysis. The modified poly[9-(4-nitrophenylsulfonyl)-9H-car- bazole] [poly(NPhSCz)] on a gold electrode and CFME was characterized in different initial monomer concentrations by cyclic voltammetry (CV), FTIR–atte- nuated total reflection (ATR) spectroscopy, scanning electron microscopy (SEM)–energy-dispersive X-ray analysis (EDX), and EIS. Poly(NPhSCz) on a gold electrode and CFME thin films were synthesized in the equivalent circuit model of R[QR(CR)(RW)](CR), where R: Current, Q: Constant phase element, C: Double layer capacitance, W: Warburg impedance. Correspondence to: M. Ates (mates@nku.edu.tr). Journal of Applied Polymer Science, Vol. 124, 4655–4662 (2012) V C 2011 Wiley Periodicals, Inc.