Conversion of polyaniline from insulating to conducting state in aqueous viologen solutions

The interactions of polyaniline coatings on low-density polyethylene films with aqueous viologen solutions were investigated. The coatings were characterized by X-ray photoelectron spectroscopy, electron spin spectroscopy, UV-visible absorption spectroscopy and sheet resistance measurements. The results showed that the polyaniline coating can be converted from the insulating base form to the electrically conducting salt form after reaction with the viologen solutions. The reaction rate is dependent on the intrinsic oxidation state of the polyaniline, the type and concentration of the viologen, and the reaction temperature. It is proposed that the conversion of the polyaniline to a conductive state occurs via an oxidative doping mechanism whereby electrons are transferred to the viologen dications. In the proposed mechanism, dissolved oxygen is deemed to play an important role, and this was verified experimentally.