Quantum Mechanical Computations and Microkinetic Modeling to Obtain Mechanism and Kinetics of Oxidative Degradation of a Polyimide

Improving the high-temperature long-term thermo-oxidative stability of high-performance polymers is crucial for their applications in aerospace industry. For designing novel polymers with improved oxidative stability, it is vital to identify the most reactive moiety of the polyimide toward oxidation and understand the mechanism of oxidation. Quantum chemical calculations and microkinetic analysis have been carried out here to obtain the molecular level details of the oxidative degradation of a commercially important polyimide, PMR-15, at high temperatures. This study identifies the most vulnerable moiety of PMR-15 toward oxidation. Moreover, the rate-determining step in the oxidative degradation is also scrutinized. Mechanistic understanding of the reaction leads us to propose new modifications of PMR-15 with a better thermo-oxidative stability.