Molecular Mechanisms of Strength and Toughness in Slide-Ring Polymer Networks: Insights from Coarse-Grained Molecular Dynamics Simulations.

Slide-ring (SR) polymer networks consist of cyclic molecules threaded onto polymer axial chains as movable cross-links, giving rise to exceptional extensibility and toughness. Yet, their mechanical response and fracture mechanisms remain unclear, particularly regarding how ring number, chain length, and cross-link number act in concert. Here, we use coarse-grained molecular dynamics simulations to systematically probe how these parameters govern deformation and failure in SR networks. We show that ring sliding is central to their mechanical performance, such as ultimate strength and toughness. Increasing ring number reduces ultimate strength and toughness by shortening sliding distances, suppressing chain orientation, and concentrating stress at chain ends. In contrast, increasing chain length enhances toughness and strength by enlarging sliding distances, promoting chain alignment, delaying fracture, and introducing entanglements that stabilize craze-like structures. Increasing cross-link number strengthens and toughens the networks by improving connectivity and stress transfer; however, the maximum sliding distance is reached at smaller strains, leading to higher stresses at small deformations but earlier failure at large strains. Void analysis further reveals that lower ring number suppresses void formation, whereas higher cross-link density promotes more homogeneous deformation. These molecular insights clarify strength-toughness trade-offs and guide the design of next-generation SR materials.