XPS STUDY OF SELF-DOPED CONDUCTING POLYANILINE AND PARENT SYSTEMS

The structure and protonation level of sulfonated polyaniline as well as the chemically synthesized emeraldine base and its chloride salt have been investigated by X-ray photoelectron spectroscopy (XPS). The results indicate that approximately 50% of the phenyl rings of the sulfonated polyaniline have a hydrogen atom substituted by a -SO3H group. Approximately 50% of the nitrogen sites are protonated in this self-doped conducting polymer. The protonation level remains unchanged upon exposure to high vacuum at room temperature. In contrast, emeraldine hydrochloride undergoes partial deprotonation and probably reduction as well under high-vacuum conditions. The N 1s lines show there is greater charge localization in the sulfonated polyaniline system than in emeraldine hydrochloride due to the presence of -SO3- groups. The results of the XPS study are in agreement with data obtained by other techniques.