Atomic-Scale Simulations of Chemical Damage in Neoprene under Noble Gas Ion Irradiation

The molecular simulation is an effective approach for investigating the effects of energetic ion irradiation on polymers. However, there is a lack of relevant studies on atomic structural changes and quantitative analysis. This study utilizes an inelastic thermal spike model and reactive molecular dynamics simulations to investigate the damage mechanisms of noble gas ion irradiation in neoprene rubber. The ion track structure and chemical damage mechanism are systematically studied. The radiolytic products are observed to form a distinctive core-shell structure with a threshold in electronic energy loss (S_e). Subtle chemical structural changes are noted in the track shell, in stark contrast to the pronounced damage observed in the track core. Additionally, the four distinct types of repeating units in the neoprene molecular chain are found to significantly influence both the structure and the yield of the radiolytic products. The extent of chemical damage is further quantitatively analyzed. A remarkable linear relationship is verified between damage cross sections (σ) and S_e. Moreover, the activation energy associated with the same chemical structure is found to remain constant. These results are in alignment with previous experimental studies. This work provides an effective and accurate simulation method for studying radiolytic mechanisms in polymers.