Study of polypyrrole aging by XPS, FTIR and conductivity measurements

Abstract

Five different polypyrroles (PPys) with four different oxidants, namely, FeCl3, FeCl3·6H2O, Fe2(SO4)3, and (NH4)2S2O8, were prepared by chemical oxidative polymerization and studied during aging. In the case of FeCl3, 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 FeCl3 and FeCl3·6H2O 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 Fe2(SO4)3 and (NH4)2S2O8 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.