Storage characteristics of polyanilines. An investigation by cyclic voltammetry and impedence spectroscopy.

The stability of pure polyaniline films prepared by cyclic voltammetry in a sulfuric solution has been tested by long-term storage under different conditions. The samples were kept for up to several days, on open circuit, in different solutions or in air. At selected storage times, cyclic voltammetry and impedance spectroscopy tests were run. A particularly severe degradation was observed in pure H2O, in LiClO4-PC and upon exposure to air. Degradation was also observed in a 1 M H2SO4-0.5 M Na2SO4 solution. This contradicts previous inferences of a lack of hydrolysis reactions, leading to quinone formation, at open circuit iri acidic solutions. Certainly, the degradation proceeds much faster if a potential of 0.7 V versus SCE is applied for some time. Five ring-substituted anilines, o- and m-toluidine, o- and m-sulfonic aniline and o-anisidine, have been polymerized with the same technique. Their degradation has been evaluated in an aqueous acidic solution and in two organic solutions based on PC and THF, respectively. The degradation of these substituted polyanilines is favoured by electron donor substituents and by protophilic solvents.