Materials Science Communication Studies on poly(diphenylamine) synthesized electrochemically in nonaqueous media A.A. Athawale * , B.A. Deore, V.V. Chabukswar Department of Chemistry, University of Pune, Pune 411007, India Received 7 August 1998; received in revised form 12 October 1998; accepted 9 November 1998 Abstract Poly(diphenylamine) has been synthesized electrochemically under galvanostatic condition in nonaqueous acetonitrile media at different monomer concentrations. The UV±Vis spectra reveals the selective formation of conducting phase 840 nm at a low monomer concentration of 0.05 M. An increase in monomer concentration to 0.1 and 0.4 M leads to a loss in selectivity in the formation of conducting phase (especially at a higher time interval). The characteristics observed in the IR absorption spectra are in accordance with those obtained in the UV±Vis spectra. Morphology of the ®lms exhibit a change over from ®brillar to granular type on going from a monomer concentration of 0.05 to 0.4 M. The effect of monomer concentration on the redox properties of diphenyl amine and poly(diphenylamine) are investigated using a cyclic voltammetric technique. On comparing the two sets of cyclic voltammograms, a shift in peak potential is observed. From the thermal analysis it is found that the loss in second step is greater at lower monomer concentration due to predominant formation of conducting phase. # 1999 Elsevier Science S.A. All rights reserved. Keywords: Poly(diphenylamine); Monomer concentration; Nonaqueous media; Conducting phase 1. Introduction Polyaniline and its substituted derivatives have been studied exhaustively due to their exotic properties and novel applications in industries [1±6]. The substituted derivatives of polyaniline have certain advantages i.e. they are easily processible and bear good mechanical strength compared to pure polyaniline. Among the substituted derivatives two types are observed; one is ring substituted and the other are N-alkyl and aryl substituted derivatives. The N-substi- tuted derivatives exhibit an additional property of having conductivity comparable to that observed for polyaniline. These N-aryl substituted polymers represent a new class of conducting polymers intermediate between polyaniline and poly(phenylene). Usually, they are synthesized in aqueous media using protonic acids such as HClO 4 ,H 2 SO 4 , HCl etc. However, such a media poses a serious problem of over oxidation of the polymer or its decomposition. These limita- tions can be overcome to a certain extent by synthesizing the polymer in a nonaqueous media [7±10], also, the processi- bility of the polymer is enhanced. Therefore, in the present work, we have chosen to synthe- size polydiphenylamine which constitutes N-aryl type of substituent. The mechanism of polymerization in this class differs from that observed in polyaniline and its ring sub- stituted derivatives. In polyaniline and its ring substituted derivatives, the preferential head±tail polymerizationmechan- ism is observed. On the contrary, in diphenylamine, poly- merization is known to proceed through 4±4 0 coupling. This probably leads to the difference in the properties of this poly- mer. We have tried to give a detailed account of the studies on this polymer synthesized by electrochemical method in acetonitrile media. The properties were investigated using UV±Vis, IR spectroscopy, scanning electron microscopy, cyclic voltammetry and thermogravimetric analysis. 2. Experimental All the chemicals used were of AR grade. The electrolyte solution (0.05, 0.1 and 0.4 M) were prepared by adding appropriate amount of monomer in acetonitrile containing 0.1 M tetraethyl ammonium perchlorate (TEAP) as a sup- porting electrolyte. Three electrode system comprising of SnO 2 : F coated corning glass [11] (sheet resistance 10 ) as a working electrode and Pt and SCE as counter and reference Materials Chemistry and Physics 58 (1999) 94±100 *Corresponding author. Fax: +91-212-353899; e-mail:agbed@chem.- unipune.ernet.in 0254-0584/99/$ ± see front matter # 1999 Elsevier Science S.A. All rights reserved. PII: S0254-0584(98)00258-2