Molecular simulation of an initial stage of the ordered-structure formation of linear and ring polymers upon cooling from the melts

Monte Carlo (MC) simulation of the coarse-grained ring and linear polyethylene (PE) models were employed to study the early stage of the ordered-structure formation upon cooling from the melts. The simulations suggest that the ordered structure with the single domain can be formed for both linear and ring PE chains which have the same mean square radius of gyration in the molten state. Molecular and structural properties evaluated from the simulation are the fraction of trans conformation and the sequence length of trans state, the anisotropic change of chain dimension, the overall orientation corre-lation function, intra-and inter-molecular bond orientation correlation functions and intermolecular pair correlation function. All these properties reveal an ordering process as the sign of crystallization espe-cially for linear chains whereas it is more difficult for ring polymer to form an ordered phase. For ring chains, the ordered structures were formed with multiple folded conformations and smaller magnitude for the fraction of trans conformation, chain orientation, degree of chain packing, intra-and inter-molecular bond ordering. The simulations suggest that PE chains are needed to stretch to some extent before the chain alignment can proceed. Compared to the linear polymers with comparable molecular size, ring PE chains tend to form the less-ordered crystalline structure, have higher melting temperature and exhibit slower crystallization rates.(c) 2022 Elsevier B.V. All rights reserved.

Automated summary

Monte Carlo simulations were used to study the early stage of ordered-structure formation in linear and ring polyethylene chains. The simulations revealed that both linear and ring chains can form an ordered structure, but it is more difficult for ring chains. Molecular and structural properties indicated an ordering process and the need for stretching in ring polymer alignment.