Study of polypyrrole aging by XPS, FTIR and conductivity measurements.

Five different polypyrroles (PPys) with four different oxidants, namely, FeCl 3 , FeCl 3 ·6H 2 O, Fe 2 (SO 4 ) 3 , and (NH 4 ) 2 S 2 O 8 , were prepared by chemical oxidative polymerization and studied during aging. In the case of FeCl 3 , the anionic surfactant dodecylbenzenesulfonic acid (DBSA) was used as a co-dopant to improve the stability. The prepared PPys were aged (>400 days) in ambient air at a temperature of 24 ± 2 °C in our laboratory, where they were not directly exposed to the sun. A clear increase in the oxygen content could be seen on the surface of all the prepared samples. There was no significant difference between PPy prepared using FeCl 3 and FeCl 3 ·6H 2 O as oxidants. The incorporation of the anionic surfactant dodecylbenzenesulfonic acid into the PPy structure did not lead to a longer effective conjugation length but did lead to the superior stability of the prepared PPy in ambient air. PPy prepared with Fe 2 (SO 4 ) 3 and (NH 4 ) 2 S 2 O 8 showed inferior stability of electrical conductivity among the samples studied. The samples were characterized by X-ray photoelectron spectroscopy (XPS), Fourier transformed infrared spectroscopy (FTIR), and elemental analysis (EA), and the chemical changes during aging were confronted with measurements of the electrical conductivity. [ABSTRACT FROM AUTHOR]