Insights into the oxidative thermal stability of mesoporous triazine-based organic polymers: Kinetics and thermodynamic parameters

Abstract

This study investigates the thermal degradation kinetics of mesoporous triazine-based polymers, namely triazine-amine and triazine-ether polymers. The synthesis, physicochemical characterization, and catalytic applications of these polymers were discussed in our previous report. Herein, the thermal stability parameters, including kinetic triplets and thermodynamic parameters, were determined using thermogravimetric analysis (TGA) and non-isothermal mathematical approximations such as Coats-Redfern, Broido, and Horowitz–Metzger methods. Triazine-ether polymers exhibit thermal stability within the range of 200°C–300°C, while triazine-amine polymer demonstrates superior thermal stability, reaching up to 450°C. According to the Coats-Redfern method, the degradation follows reaction orders of 0.5 ≤ n ≤ 1. The activation energy of triazine-amine polymer is notably high, particularly at the third degradation stage (e.g., 89.0 kJ/mol by the Broido method), attributed to its high nitrogen content. Conversely, the higher carbon content of triazine-ether polymers reduces their activation energy to approximately 30 kJ/mol at all stages and thus, facilitates the degradation process. Thermodynamically, the degradation process is favorable yet non-spontaneous, with intermediate states of the polymers exhibiting higher entropy, indicative of their enhanced degradation capability.