Modeling reaction pathways of low energy particle deposition on polymer surfaces via first principle calculations

The chemical processes that lead to polystyrene surface modification via low energy deposition of C₂H⁺, C₂F⁺, CH₂, CH₂⁺, and H⁺ radicals and ions are examined using first principles calculations. Specifically, the reaction mechanisms responsible for products identified in classical molecular dynamics with reactive empirical bond-order potentials are examined using density functional theory. In addition, these calculations consider how the presence of charges on the incident particles changes the result for the CH₂ system through the comparison of barriers, transition states, and final products for CH₂ and CH₂⁺. The structures of the reaction species and energy barriers are determined using the B3LYP hybrid functional. Finally, CCSD/6-31G(d,p) single point energy calculations are carried out to obtain optimized energy barriers. The results indicate that the large variety of reactions occurring on the polystyrene surface are a consequence of complex interactions between the substrate and the deposited particles, which can easily be identified and characterized using advanced computational methodologies, such as first principle calculations.