Raman spectroscopy of polyaniline and oligoaniline thin films

Abstract

Polyaniline or oligoanilines were deposited in situ as thin films on non-conducting silicon supports during the chemical oxidation of aniline with ammonium peroxydisulfate in various aqueous media. When the polymerization was carried out in the solution of strong (sulfuric) acid, polyaniline films having a globular morphology were obtained. In the solutions of weak (acetic or succinic) acids or in water, the films composed of polyaniline nanotubes were produced. The oxidation of aniline under alkaline conditions yielded aniline oligomers with microspherical morphology. Infrared spectra suggest that the oligomers produced at the beginning of the oxidation are similar regardless of the acidity of the medium, but this method was not able to elucidate the details of their molecular structure. A new insight into the structure of the early products of aniline oxidation based on their Raman spectra is reported. The influence of smooth gold support on the Raman spectra of the films has also been studied.