Diffusion of hydrogen and its isotopes in polystyrene-Cu interface

In order to explore the diffusion of gas in the polymer chain and solid surface, molecular dynamics (MD) method is used to simulate the diffusion of H2, D2, T2 in the interface of polystyrene-Cu (PS-Cu). Their diffusion coefficients are obtained from the mean square displacement (MSD) of these gases in different metal surfaces and polystyrene interfaces. Results show that the diffusion coefficients of these gases in the interface are smaller than those in polystyrene itself, and the diffusion coefficients of these gases in PS-Cu (110) interface are the largest, while in PS-Cu (111) interface they are the smallest. Through calculation and analysis of interaction between PS and metal surface, we also found that the bigger the interaction energy is, the smaller the diffusion coefficient of gas in the interface becomes. Moreover, crystal density of the metal surface has a certain effect on the diffusion of gas in the interface.