A kinetic analysis of thermal decomposition of ortho-substituted polyaniline derivatives

A plethora of studies in conjugated polymer modification is aimed at improving their physicochemical properties for practical application. Functionalization of polyaniline (PANI) by introducing a substituent on the aromatic ring is an effective way to achieve high solubility. In this regard, this study was focused on the investigation of the thermal stability of three PANI derivatives with ortho-substituents of various structures using thermogravimetric analysis at different heating rates (5, 10, 15, and 20 °C min⁻¹) in a nitrogen atmosphere. The results of TGA and DTG showed that the process of thermal degradation of PANI derivatives proceeded according to a complex multistage mechanism. Using the Coats–Redfern integral method and 10 basic models, activation energies and pre-exponential factors were calculated for three stages of polymer thermal degradation. According to the results, with the highest linear regression coefficient, the second-order reaction model (F2) was the most suitable for the initial period of decomposition, while diffusion (D1, D2, D3) and interfacial (S1, S2) models were suitable for high-temperature stages. All models showed a positive ΔH. The highest ΔG values were obtained using diffusion and interfacial models.