Characterization of chemically synthesized polyanilines treated with tetrafluoroborate salts. A comparative study

Abstract

A series of polyanilines (PANI) prepared chemically in the presence of different tetrafluoroborates (NaBF4, NO2BF4, and Et4NBF4) has been characterized by x-ray photoelectron spectroscopy (XPS), infrared spectroscopy (IR), and elemental analysis. The results suggest that only PANI-NO2BF4 exhibits conductivity comparable to those PANI's protonated with strong acids. No significant interaction between the tetrafluoroborate salt and the polyaniline was found in the PANI-NaBF4 and PANI-Et4NBF4 systems due to the weak hydrolytic ability of the cations. In the case of PANI-NO2BF4, the salt rapidly hydrolyzes to give HBF4 with liberation of NO2 in the aqueous polymerization medium. This can then act as an effective protonating agent in the same fashion as HCl or HBr normally used for increasing the conductivity of PANI's. We have shown that the differences between a conducting and an insulating polymer can be revealed by IR spectroscopy and XPS. Together, these techniques are very useful in assessing and screening novel chemical agents used to improve conductivity over the existing PANI's.