Pressure-Induced Reactivity in the Emeraldine Salt and Base Forms of Polyaniline Probed by FTIR and Raman

This report presents the influence of the morphology on the pressure-induced reactivity of the doped (PANI-ES) and dedoped (PANI-EB) forms of polyaniline using Raman and FTIR techniques. Our PANI-EB FTIR spectroscopy data showed an intensity exchange among characteristic bands of the quinoid and benzoic segments above 9 GPa, suggesting a specific coupling reaction between adjacent quinoid rings. The reaction kinetic was followed, and the results showed a dependence of the rate constant with pressure, as well as the activation volume, presented an inversion from negative to positive at 13 GPa, suggesting that steric factors have a role in the reactivity of the species. Raman spectra of PANI-ES showed a broadening and a blue shift of the bands as the pressure increases preceding the almost complete amorphization of the polymer; after decompression, some minor spectral changes were observed, suggesting the occurrence of the dedoping and cross-linking reactions in less extension than PANI-EB.