Conformational transition in polyaniline films - Spectroscopic and conductivity studies of ageing

Polyaniline films were produced in situ at room temperature from aniline hydrochloride oxidized with ammonium peroxydisulfate on glass surfaces immersed in an aqueous reaction mixture. A notable change in the character of the time dependence of resistivity at fixed temperature was observed when the temperature of ageing exceeded 85 °C. The ageing was much faster above this limit. This observation is reflected in the FTIR spectroscopic measurements on the aged protonated, as well as deprotonated, samples. The FTIR spectral variation may be explained by a conformational transition of the polymer chain at about 85 °C. The fact that a similar transition has been found with deprotonated samples indicates that this feature is an inherent property of polyaniline, and is not caused by the acid component of the PANI salt.