Molecular dynamics simulation of nonisothermal crystallization of a single polyethylene chain and short polyethylene chains based on OPLS force field

Abstract

Molecular dynamics simulations on the nonisothermal crystallization of a single polyethylene chain and short polyethylene chains based on the all-atom model and optimized potentials for liquid simulations-all atom (OPLS-AA) force field are conducted in this article. Four all-atom single chain models with different chain lengths (C1000, C2000, C3000, and C4000) and four all-atom short chain models with the same chain length and different number of chains (2C500, 4C500, 6C500, and 8C500) are constructed. The collapse process at a high temperature of 600 K and the nonisothermal crystallization process with different cooling rates at the temperature range of 600–300 K are simulated. Roles of chain length, number of chains, cooling rate on the potential energy, van der Waals (V dw) energy, radius of gyration, root mean square deviation, and crystallinity are explored. By comparing with the existing results obtained by the united atom model, the validity and accuracy of this study are proved. Results show that in the collapse process, the chain length is the major factor, whereas the cooling rate has the greatest influence during the nonisothermal crystallization process. As the cooling rate decreases, a “platform” appeared in the V dw energy curve, which has a profound impact on the crystallization.

Keywords

• molecular dynamics
• polyethylene crystallization
• opls-aa force field
• all-atom model