Molecular Dynamics Simulation of Nano-ZnO Cluster’ Diffusion in Polyethylene

Abstract

This work is intended to simulate and analyze the diffusion process and the diffusion mechanism of nano-ZnO cluster in low density polyethylene (LDPE) using the molecular dynamics (MD) simulation method. MD simulations were carried out at three different temperatures (293 K, 313 K and 343 K) in two models including single cell of ZnO-LDPE chain (ZL cell) and two-phase of ZnO-LDPE/water molecular (ZL-W cell). The diffusion coefficient of nano-ZnO (DM) is obtained by calculating the slope of mean square displacement according to the Einstein relationship. DM of ZL cell and ZL-W cell were 0.17×10-8~3.5×10-8 cm2 s-1 and 6.33×10-8~2.38×10-6 cm2 s-1 respectively. This result implied that DM could be increased by the presence of water molecular phase. Moreover, the fractional free volume (FFV) and the movement trajectories of ZnO cluster were discussed. It demonstrated that the FFV was enlarged with the temperatures and the oscillation of nano-ZnO cluster was wider in ZL-W cell than ZL cell. The relationship between DM and temperature satisfied the Arrhenius equation.