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

Yunlong Lv,Chunlei Ruan

doi:10.1515/epoly-2022-0019

Yunlong Lv, Chunlei Ruan

Open Access

https://doi.org/10.1515/epoly-2022-0019

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Journal: e-Polymers	Publication Date: Jan 28, 2022
Citations: 3	License type: CC BY 4.0

Affiliation: Henan University of Science and Technology

Abstract

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.

Highlights

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
In the collapse process of short polyethylene chains with short length (8C500) as shown in Figure 2b, the chains fold from the extended state gradually and crimple into a random coil
Molecular dynamics simulations on the nonisothermal crystallization of a single polyethylene chain and short polyethylene chains based on the allatom model and OPLS-AA force field were conducted

Summary

Introduction

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. Kavassalis and Sundararajan [3,4] constructed molecular dynamics simulations of a series of short chains (30, 60, 100, 150, 200, 250, 500, 750, and 1,000 CH2) to study the collapse and crystallization of polyethylene. They treated the methylene group as a unit through the united atom (UA) approximation. The all-atom model and optimized potentials for liquid simulations-all atom (OPLS-AA) force field were used to simulate the process of collapse and nonisothermal crystallization of a single polyethylene chain and short polyethylene chains. Results were compared with the published literatures in which UA models were used

Model and force field

Problem definition

Results and discussion

Conclusion