Heterophase Reduction of the Fully Oxidized Aniline Tetramer

Abstract

Electrically conductive polyaniline (PANI) is ubiquitously applied in energy storage devices using its three oxidation states and reversible doping and dedoping processes. However, the chemical stability of the most oxidized state, the pernigraniline base, has gained considerably less interest than its emeraldine base counterpart. By utilizing the phenyl-capped aniline tetramer (TANI) as a model of PANI, this work examines the heterophase reductions of the pernigraniline base. Through UV–vis spectroscopy and electrochemical methods, we provide both a quantitative and qualitative analysis, demonstrating the dependence of the reduction rate on acidity, as corroborated with cyclic voltammograms and open circuit potential measurements. Solid state reactions reveal that reduction can be achieved via ball milling with a solid acid, the piezoelectric material BaTiO₃, and cadmium metal pieces. This behavior was also applied to thin films, enabling the patterning via a responsive and irreversible vapor reduction.