Poly(2-aminobiphenyl), Preparation, Characterization, Mechanism, and Kinetics of the Electropolymerization Process Waheed A. Badawy, Khaled M. Ismail, Ziad M. Khalifa, Shymaa S. Medany Chemistry Department, Faculty of Science, Cairo University, Giza, Egypt Received 23 August 2011; accepted 29 November 2011 DOI 10.1002/app.36621 Published online in Wiley Online Library (wileyonlinelibrary.com). ABSTRACT: Electropolymerization of 2-aminobiphenyl was carried out on glassy carbon, gold, and platinum elec- trodes, in aqueous–organic solvent mixtures, using a potentiodynamic technique. The choice of organic solvent strongly influences the film formation. In a mixture of 60% acetonitrile and 40% 1.0M HClO 4 , stable films were obtained. The poly(2-aminobiphenyl) films were character- ized with cyclic voltammetry, where the electrochemical activity of the formed polymer films was investigated in acidic and neutral aqueous solutions containing perchlo- rates or in potassium ferrocyanide. The prepared films posses a remarkable stability in acidic aqueous solutions and are also stable in some organic solvents. The stability of the polymer films depends on the pH of the solution, and the mechanism of the polymerization process involves deprotonation and head-to-tail coupling of oxi- dized monomers with its oligomeric radical cations. The kinetics of the electropolymerization process was investi- gated by determining the charge consumed during the electropolymerization as a function of time at different concentrations of the electrolyte components. The electro- polymerization process follows first-order kinetics with respect to the monomer and negative order with respect to HClO 4 . V C 2012 Wiley Periodicals, Inc. J Appl Polym Sci 000: 000–000, 2012 Key words: conducting polymers; polymerization; cyclic voltammetry; poly(2-aminobiphenyl) INTRODUCTION The study of electrodes modified with thin polymer films formed by electropolymerization of simple or- ganic substances is a field of continuous interest in electrochemistry. 1–3 The electropolymerized conduc- tive films have promising applications in lightweight (rechargeable) batteries, 4,5 electrochromic display devices, 6–8 biosensors, 9,10 and corrosion protection. 11 Some of these polymer films have shown good sta- bility in aqueous media and normal atmospheric conditions. 12 Electrochemical polymerization of sim- ple aromatic amines is usually done in acidic solu- tions to obtain a high degree of polymerization and to avoid NAN coupling. 13,14 Amino compounds can rather easily be polymerized in aqueous 1.0M HClO 4 solutions. 15 The polymerization in organic solvents is more difficult due to the high solubility of the reaction product and formation of very stable inter- mediates resulting in poor film formation. 16,17 Elec- tropolymerization in aqueous–organic solvent mix- tures overcomes the solubility problem of the reaction product. There are only few reports on the polymerization of PANI and related compounds in aqueous–organic solvent mixtures. 18–20 While the electropolymerization of unsubstituted aromatic amines has received a great deal of atten- tion, the electropolymerization of the aryl-substi- tuted aniline, especially o-substituted monomers, has got much less attention. Poly(4-aminobiphenyl) has been prepared successfully from solutions contain- ing 0.02M 4-aminobiphenyl in a mixture of 2.0M HCl and acetonitrile (ACN; 68: 32 volume/vol- ume). 21 The polymerization of 2-aminobiphenyl, in which a phenyl group is present in the o-position of the aniline moiety, seems to be an important subject for intensive investigation. The polymer film is expected to be stable in aqueous acidic solutions with an electroactive response in a wide potential range. It may possess electrochromic properties for some beneficial applications. Many studies have been carried out to clarify the kinetics of the electropolymerization processes. 22–29 The study of the reaction order with respect to the monomer and the electrolyte in the electropolymeriza- tion process is an important issue. This study provides information about the nature of the reaction taking place at the electrode surface and the chemical struc- ture of the polymer film beside the ways to improve its physical properties, e.g., its electrical conductivity. Correspondence to: W. A. Badawy (wbadawy50@hotmail. com or wbadawy@cu.edu.eg). Journal of Applied Polymer Science, Vol. 000, 000–000 (2012) V C 2012 Wiley Periodicals, Inc.