Interaction of polyaniline film with dibutyl phosphonate versus phosphite: Enhanced thermal stability

Interaction between blue film of polyaniline base with dibutyl phosphonate yields green polyaniline film. This resembles the classical protonation of polyaniline base with acids but, in the contrast, there is no proton available in prevailing phosphonate tautomeric form. The character of interaction was studied by evolution of the infrared spectra of the film recorded during heating up to 200 °C. The experiments demonstrate that dibutyl phosphite, and not its phosphonate tautomeric form, interacts with polyaniline base. Above 140 °C, the original polyaniline base is recovered in dry air purged environment in spectrometer. The interaction with polyaniline base prevents dibutyl phosphite from the oxidation into dibutyl phosphate which occurs in case of heating of neat dibutyl phosphite, in which phosphonate form predominates. The thermal stability and the changes in molecular structure have been assessed by UV-visible, FTIR and Raman spectra. The model of the interaction based on the quantum-chemical optimization of the idealized structure is proposed.