Influence of additive-polymer interactions on the mechanical behaviors of cross-linked polymers

WJ Nie and L Xu and WJ Xia, EXTREME MECHANICS LETTERS, 80, 102403 (2025).

DOI: 10.1016/j.eml.2025.102403

Attaining an in-depth understanding of the underlying factors dictating mechanical and macroscopic properties is crucial for establishing structure-property relationships in cross-linked thermosetting polymers. The introduction of additives into these polymers can lead to significant alterations in topology, dynamic behavior, and mechanical properties. In this study, we employ a coarse-grained (CG) polymer model to systematically explore the influences of additive-polymer intermolecular interaction strength (epsilon(ap)), additive mass fraction (m), and cross-link density (c) on the temperature-dependent mechanical behaviors of a cross-linked glass-forming thermoset. Our results demonstrate that the mechanical characteristics, particularly the tensile and shear moduli, are predominantly affected by epsilon(ap) and m, with a clear temperature dependence across the glassy regime. The modulus outcomes reveal contrasting trends between the neutral interaction system ( epsilon(ap) =1) and the strong interaction system ( epsilon(ap)> 1). Intriguingly, varying Bap yields distinct scaling relationships between modulus and reduced temperature T/T-g, indicating a shift from the behavior typically observed in cross-linked thermosets without additives. Moreover, we identify a correlation between the moduli and the Debye-Waller parameter < u(2)>, providing insight into the local stiffness at the molecular level. Our results highlight the critical role of additives and their intermolecular interactions with polymers in governing the mechanical responses of crosslinked network, offering insights for molecular design of thin films, coatings, and nanocomposite systems.

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