Abstract: Taking polyethylene as the research object, based on molecular dynamics simulation, the effects of molecular chain length, main-chain segment activity, terminal group activity and molecular chain orientation on the diffusion behavior of oxygen molecules (O2) in polyethylene were studied from the aspects of temperature, structure and diffusion activation energy. Based on the COMPASS force field, a diffusion model (O2 / PE) with three-dimensional periodic boundary is constructed, optimize the model and then take molecular dynamics simulation on the stabi-lity configuration. The results show that the polymer chain movement has a great influence on the diffusion behavior of the gas. The correlation analysis between the polymer chain terminal group MSD and end-to-end distance and the diffusion coefficient shows that, the "diffusion channel" increases and the molecular diffusion rate increases when the activity of the main chain and the movement ability are enhanced. Short chain acti-vity is higher than long chain, and the flexibility is lower than that of long chain. The shorter the molecular chain is, the lower the collision frequency is, and the free volume of molecular transition increases and the diffusion rate increases. Further, a tensile load is will make the polymer chains oriented in the load direction, reduce the symmetry of the unit cell and increase the molecular diffusion rate significantly.
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