Initiation mechanisms and kinetic analysis of the isothermal decomposition of poly(alpha-methylstyrene): a ReaxFF molecular dynamics study

This study investigates the thermal decomposition initiation mechanisms and kinetics of poly(alpha-methylstyrene) (PaMS) under isothermal conditions, using molecular dynamics simulations with the ReaxFF reactive force field. The unimolecular pyrolysis simulations show that the thermal decomposition of the P alpha MS molecule is initiated mainly by carbon-carbon backbone cleavage in two types at random points along the main chain that leads to different intermediates, and is accompanied by depolymerization reactions that lead to the formation of the final products. The time evolution of typical species in the process of P alpha MS thermal decomposition at various temperatures presents specific evolution profiles and shows a temperature-dependence effect. Isothermal decomposition kinetic analysis based on P alpha MS pyrolysis shows that the activation energy varies with the degree of conversion during the thermal decomposition processes, which infers that the decomposition process at different conversions may have different reaction mechanisms.