Poly(o-aminophenol) electrosynthesized onto Platinum at acidic and neutral pH: comparative investigation on the polymers characteristics and on their inner and outer interfaces

The polymer formed by electrochemical oxidation of o-aminophenol (oAP) on platinum substrates, both in neutral and acidic media, has been characterized. Attention was focussed on the three constituent phases: the polymer itself and its inner (metal/polymer) and outer (polymer/electrolytic solution) interfaces. As well known, poly(o-aminophenol) (PoAP) consistently shows tuneable properties depending on pH, evidencing a remarkable electroactivity or a strong passivating behaviour if synthesized in acidic and in neutral/basic media, respectively. Although much investigated, a full understanding of the polymerization routes has not yet been reached for either the conducting and insulating films. To improve this situation studies on PoAP were conducted with a combination of techniques: Cyclic Voltammetry (CV); X-ray Photoelectron Spectroscopy (XPS); Atomic Force Microscopy (AFM); and micro-Raman. It was thus possible to compare compositional and morphological analyses, highlighting in turn different analytical depths of our PoAP/Pt systems. The results here obtained add new information on how to recognize the influence of platinum oxidation and its cleanliness on interface reactions. It was also found that, in order to estimate properly the real structure of both insulating and conducting PoAP, the presence of oxidized terminal groups and water molecules strongly bonded along the polymer chains must be taken into account.