Solid-state oxidation of aniline hydrochloride with various oxidants

Aniline hydrochloride was oxidized in the solid state with three different oxidants: ammonium peroxydisulfate, iron(III) chloride, and silver nitrate. Polyaniline salt was obtained after a few hours when ammonium peroxydisulfate was used as an oxidant. The polymerization of aniline hydrochloride with silver nitrate leads to polyaniline only after several days; in the case of iron(III) chloride, aniline oligomers were obtained. The conductivity of the polyaniline was 0.21 S cm−1 when ammonium peroxydisulfate was applied; it is comparable with the conductivity of a ‘standard’ polyaniline. The oxidation with silver nitrate yields a composite material, polyaniline salt and silver particles, with conductivity 1.5 × 10−3 S cm−1. Photoacoustic spectroscopy was employed to study the kinetics of the oxidation reaction. Infrared and UV–vis spectra were efficient tools to characterize the final products, and to compare their molecular structure with that of the polyaniline prepared under ‘standard’ conditions in aqueous medium.