Chemical Modification of Polyaniline by N-Grafting of Polystyrene Synthesized via ATRP Homa Gheybi, Mojtaba Abbasian, Peyman Najafi Moghaddam, Ali Akbar Entezami Laboratory of Polymer, Faculty of Chemistry, University of Tabriz, Tabriz, Iran Received 26 February 2007; accepted 10 July 2007 DOI 10.1002/app.27037 Published online 22 August 2007 in Wiley InterScience (www.interscience.wiley.com). ABSTRACT: The N-substituted polyaniline (PANi) was synthesized by incorporation of bromine-terminated poly- styrene (PS-Br) onto the emeraldine form of polyaniline. End brominated polystyrene was synthesized by atom transfer radical polymerization (ATRP) technique and then deprotonated polyaniline was reacted with PS-Br to pre- pare PS-grafted PANi (PS-g-PANi) copolymer through N- grafting reaction. The degree of N-grafting can be con- trolled by adjusting the molar feed ratio of PS-Br to the number of repeat units of PANi. The microstructure and compositions of the PS-g-PANi copolymers with different degrees of N-substitution were characterized by FT-IR, ele- mental analysis, differential scanning calorimetry (DSC), and scanning electron microscopy (SEM). The cyclicvol- tammetry shows that the electroactivity of N-substituted PANi is strongly dependent on the degree of N-grafting. The solubility of PS-g-PANi copolymers in common or- ganic solvents such as tetrahydrofuran and chloroform was improved by increasing the degree of N-grafting, and also the samples are partially soluble in xylene. Ó 2007 Wiley Periodicals, Inc. J Appl Polym Sci 106: 3495–3501, 2007 Key words: conducting polymer; polyaniline; polystyrene; ATRP; N-substitution INTRODUCTION Polyaniline has been the subject of considerable sci- entific inquiry because of its unique electrical behav- ior, its potential as an environmentally stable con- ducting polymer 1 and wide applications in different fields, such as microelectronics, 2,3 sensors, 4,5 electro- des, 6,7 corrosion protection, 8,9 and release devi- ces. 10,11 Polyaniline is inherently brittle and poor in processability due to its insolubility in common or- ganic solvents. Its poor solubility has limited the industrial applications of polyaniline (PANi). 12,13 To improve its processability, various procedures have been adapted. For example, self doped PANi with sulfonic acid groups substituted onto the poly- mer 14,15 have been synthesized. Several ring- and N-substituted PANi, soluble in common organic sol- vents, have been prepared directly from polymeriza- tion of the corresponding aniline monomers. 16–18 The incorporation of the side groups into polyaniline has enhanced its solubility and processability and changed its properties. 19,20 Hosseini was reported the growing of aniline onto functionalized polysty- rene. 21 Another approach toward soluble polyaniline is copolymerization of aniline with a suitable substi- tuted aniline to produce copolymers. The obtained copolymers have improved in solubility. 22 To im- prove melt and solution processability, the majority of polyaniline modifications to date have been made by the incorporation of substituents on the polymer backbone. 13 Flexible alkyl chains, 23 poly(ethylengly- col) chain, 24 and polyether chain 25 have been incor- porated onto PANi through N-alkylation method. In this article, a new N-substituted PANi is synthesized by insertion of bromine-terminated polystyrene (PS- Br) onto the polyaniline backbone. Polystyrene is gaining wide recognition as it possesses many unique properties, such as solubility in organic sol- vents and good mechanical properties. Thus, incor- poration of polystyrene into polyaniline may endow the resulted copolymer with new and interesting properties. For instances, the process may enhance the solubility and the processability of polyaniline. PS-Br was synthesized via atom transfer radical po- lymerization (ATRP) technique. 26–29 EXPERIMENTAL Materials Aniline from Merck was distilled twice under a reduced pressure before use. Styrene from Tabriz pe- trochemical company was distilled under a reduced pressure. Ammonium persulfate (Merck) was recrys- tallized at room temperature from EtOH/water. 2.2 0 - bipyridine (Merck) was used as received. Copper (I) chloride (Merck) was purified by stirring in glacial Correspondence to: A. A. Entezami (aaentezami@yahoo. com or aentezami@tabrizu.ac.ir). Journal of Applied Polymer Science, Vol. 106, 3495–3501 (2007) V V C 2007 Wiley Periodicals, Inc.