Electrochromic properties of sulfonic acid ring-substituted polyaniline in aqueous and non-aqueous media

It is a simple way to prepare the sulfonic acid ring-substituted polyaniline (SPAn) electrode via the directly chemical reaction of polyaniline (PAn) film polymerized on the indium-fin oxide (ITO) conducting glass with the concentrated sulfuric acid. The in situ visible spectra show that the color of the SPAn film in 0.3 M Na-2 SO4 solution with pH 7.0 still changes with the applied potential. The pH range for the change in the color of the SPAn film is larger than that of polyaniline film. In 0.25 M LiClO4 propylene carbonate (PC) solution, the color of the SPAn film changes from blue via green to transparent yellow as the applied potential decreases from 0.80 to -0.20 V (Ag/AgCl with saturated KCl solution), and this change is reversible. Based on the result from the cyclic voltammogram, SPAn in the non-aqueous solution has a good electrochemical activity and a fast charge transfer characteristic. The XPS spectrum of SPAn indicates that polyaniline in the concentrated sulfuric acid can be sulfonated. (C) 2004 Elsevier B.V. All rights reserved.