Large scale polymer toughening of two-dimensional materials revealed by in situ TEM fracture tests and multiscale simulations

Y Zhang and CY Li and X Zhang and JG Wen and A Sumant and A Strachan and HD Espinosa, EUROPEAN JOURNAL OF MECHANICS A-SOLIDS, 114, 105748 (2025).

DOI: 10.1016/j.euromechsol.2025.105748

Two-dimensional (2D) materials offer significant potential for applications in energy-harvesting devices, batteries, sensors, and transistors. However, their intrinsic brittleness makes them prone to mechanical failure, limiting their practical use. In this work, we perform in situ transmission electron microscopy (TEM) fracture tests on monolayer MoSe2 and uncover an extrinsic toughening effect induced by an ultrathin adsorbed polystyrene adlayer. This adlayer substantially enhances the fracture resistance of the 2D flakes. Through a combination of molecular dynamics simulations and finite element analysis, we elucidate the molecular mechanism behind this toughening effect. It arises from the active crack-bridging behavior of entangled polymer chains and the formation of a fracture process zone that stabilizes crack propagation and increases the energy required for crack extension. The proposed toughening mechanism offers a pathway to improving the mechanical reliability of 2D material-based devices by mitigating the risk of sudden failure.

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