Fatigue of Vitrimers and Their Nanoparticle‐Reinforced Composites

Vitrimers are a class of cross‐linked polymers with dynamic covalent bonds. However, despite extensive studies on their reprocessability and self‐healing properties, research on the fatigue of vitrimers, especially on the role of dynamic covalent bonds in fatigue resistance, remains largely unexplored. Herein, we investigate the fatigue behavior of a representative disulfide‐based vitrimer by tuning bond exchange kinetics and introducing nanoparticle reinforcements. We characterized their residual strain, fatigue damage, and fatigue threshold. The results show that bond exchange kinetics strongly influence fatigue behaviors. Although a higher catalyst content accelerates the bond exchange rate, it also facilitates irreversible network rearrangement, leading to larger residual deformation and increased fatigue damage during cyclic loading. Based on these insights, the fatigue threshold was improved by 34% by incorporating nanoparticles into the optimized vitrimer matrix, reaching 115 J/m 2 . This improvement arises from the synergistic contribution of nanoparticle reinforcement and the reversible response enabled by dynamic covalent bonds.