Morphological and chemical stabilities of polypyrrole in aqueous media for 1 year

摘要

The long-term morphological and chemical stabilities of polypyrrole grains in aqueous media (1-year duration) are investigated. Polypyrrole grains doped with chloride ions or heptadecafluorooctane sulfonic acid were extensively characterized using a wide range of analytical techniques. The average sizes of the grains were 13-15 mu m and consisted of submicrometer-sized atypical primary particles. The grain size increased in the case of polypyrrole doped with chloride ions, whereas no apparent changes were observed in the case of polypyrrole doped with heptadecafluorooctane sulfonic acid after storage at pH 3 and 10. The size and morphology of the primary particles did not change for each grain system. Appreciable changes in chemical structure and surface chemistry were observed. At pH 10, dedoping occurred easily, and chloride ions and heptadecafluorooctane sulfonic acid were released from the grains in a short time (within one week). On the other hand, the dopants were released slowly at pH 3, which is likely caused by nucleophilic attack by water molecules to the polypyrrole. The release rate of the dopant was slower for polypyrrole doped with heptadecafluorooctane sulfonic acid than for polypyrrole doped with chloride ions. This finding is attributed due to the stronger hydrophobic interaction between polypyrrole and heptadecafluorooctane sulfonic acid.