Influence of Topological Segment Length on the Mechanical Properties of Semicrystalline Polyethylene: A Bias-Controlled Monte Carlo Approach

JL Ye and MH Liu and J Hu and J Oswald, MACROMOLECULES, 58, 2521-2533 (2025).

DOI: 10.1021/acs.macromol.4c02643

We integrate a biasing mechanism into the hybrid Monte Carlo method that enables the generation of semicrystalline systems with controllable topological segment length. Analysis of the generated systems revealed an entropy-driven relationship between the bridge length and the number of bridges formed. We find that bridges significantly enhance postyield hardening, and the bridge-induced hardening can be divided into four stages: relaxed, activation, engaged, and softening. The results show that lengths of bridges govern the engagement strain and thereby the onset of bridge-induced hardening; an equation is derived to predict the engagement strain based on bridges' initial configurations and the system sizes. The softening phase occurs as the covalently connected tails and loops on the other side of the crystalline stems are pulled deeply into the crystalline lamellae, weakening the anchors of bridges. Additionally, systems with longer loops form more bridging entanglements, which, like long bridges, strengthen the hardening effect during the later stages of deformation.

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