SPECTROSCOPIC INVESTIGATION ON CONDUCTING POLY(O-AMINOPHENOL) ELECTROSYNTHESIZED ON PLATINUM- ELECTRODES IN ACIDIC MEDIA

Aminophenols are interesting members of the class of substituted anilines. Within the various isomers, o-aminophenol (OAP) has attracted most attention because of its ability to form conductive polymers under electrochemical oxidation in acidic media [1]. Unlike anilines, OAP is characterized by the presence of two groups both prone to oxidation which complicates the identification of possible intermediates in the polymerization process. There is in fact a controversy in literature regarding the formation of dimeric structures by electrochemical oxidation of OAP in aqueous solutions, acting as soluble precursors of the finite polymer, POAP. Presently, it is widely agreed that POAP is a ladder polymer composed of phenoxazine units [2]. Besides a completely ring-closed structure, an open one was also formulated containing N-phenyl-p-phenylenediamine repeating units [3]. The possibility of side reaction and consequently of sideward polymerizations thus hinders the comprehension of the real structure of the film. To deepen the understanding on POAP, extensive studies using electrochemical, spectro-electrochemical, impedance measurements and other means of investigation were performed [4] . In the present work, to gain a further insight into the polymerization route of POAP, a careful investigation has been carried out by employing XPS, micro-Raman and IR as complementary spectroscopic techniques. POAP films were electro-synthesized on platinum substrate by cyclic voltammetry, CV, in acidic OAP solution (HClO4/KClO4). Following the CV profile, comparative analyses of POAP, by varying its redox state and protonation degree, were performed, highlighting different sampling areas and depths, according to the specificity of each spectroscopy. The combined results have provided information on the polymer skeleton and its inner (Pt) and outer (environments) interfaces. Notably, the analytical capability of XPS has allowed to formulate the POAP repeat sequence and to identify species adsorbed or trapped inside the polymer. [1] C. Barbero, J.J. Silber, L. Sereno, J. Electroanal. Chem 263 (1989) 333-352. [2] A.U.H.A. Shah, R. Holze, J. Electroanal. Chem 597 (2006) 95-102 [3] A. Q. Zhang, C.Q. Cui, Y.Z.Chen, J.Y. Lee, J. Electroanal. Chem 373 (1994) 115-121 [4] R. Tucceri, P. Arnal, A. Scian, ISRN Polymer Science (2012)