Theoretical study on the pyrolysis process of POSS nanocomposites based on the molecular vibration frequency

Abstract

Identifying the factors that determine the thermal stability of polymer nanocomposites with inorganic fillers is vital. This study investigates how the modulation of polyhedral oligomeric silsesquioxanes (POSSs) affects the polymer-chain thermodynamics, using a multiscale analysis that integrates reactive molecular dynamics, first-principles calculations, and classical vibrational dynamics. The intramolecular energy transfer mechanism depending on the polymer-chain vibration frequency and covalent structure was analyzed for the entire pyrolysis process. The results revealed that the low-frequency vibration of POSS is key for the superior nanocomposite thermal stability. The dual frequency of the C–Si stretching mode directly contributes to the collection and dissipation of the thermal energy contained in the crosslinked polymer chain. The ability to block exothermic reaction pathways under pyrolysis conditions was also identified. This result elucidates the mechanism by which inorganic fillers perturb the thermodynamics and thermochemistry of polymer matrices as energy transfer within molecular chains.