Spectroscopic investigation on polymer films obtained by oxidation of o-phenylenediamine on platinum electrodes at different pHs

An investigation on the structure of poly(o-phenylenediamine) (PPD) films, obtained by electropolymerization of oPD (1,2-diaminobenzene) on platinum a t different pH values, was performed by X-ray Photoelectron Spectroscopy (X PS). XPS could be used as a "bulk" technique for PPD films analysis, due to thei r extremely low thickness. The presence of different functionalities, like primary/secondary aminic, iminic and, as minor species, oxygenated groups ( carbonyl, oximes) was suggested by curve fitting of carbon (C1s) and nitrog en (N1s) XP spectra. The use of chemical derivatization reactions (CD-XPS) confirmed the presence of primary aminic and hydroxy groups, showing that N H2 groups are present in the PPD structure even at low pH values, though th eir amount increases on increasing the pH of polymerization. Optical spectroscopy in the visible region was also performed on the electr olytic solutions at the end of polymerization, suggesting a higher conjugat ion of the oPD oligomers at low pH, which indirectly confirms XPS findings on the presence of NH2 groups in the polymer.