Simulation and experimental investigations of thermal degradation of polystyrene under femtosecond laser ablation

In the present work, the underlying mechanisms of femtosecond laser ablation of atactic polystyrene with a molecular weight of 10,000 g/mol are elucidated by large-scale molecular dynamics simulations, with an emphasis on the mechanisms of thermal degradation of polystyrene. In addition, experimental investigations of thermal degradation of polystyrene chips formed in femtosecond laser ablation, as well as pristine polystyrene, are conducted under a heating environment at 500 °C with Py-GC/MS analysis. Simulation results indicate that chain entanglement is predominant to facilitate thermal degradation of polystyrene chain, which is closely accompanied with single-chain excitation. The main degradation mechanisms of polystyrene revealed by simulations include β-scission of carbon backbone, dissociation of pendant group, breaking of π bond of pendant group and evaporation of individual atoms, which qualitatively agree well with experimental results. It is also found that the laser energy has a significant influence on the degradation of polystyrene under femtosecond laser ablation.