Breaking the toughness-strength trade-off in polymer nanocomposites via a mechanically interlocked interface

Polymer nanocomposites face a fundamental challenge in simultaneously enhancing strength and toughness, as current methods often compromise one for the other. To address this issue, we have incorporated mechanically interlocked [2]rotaxane units into the interfacial layer of dynamically cross-linked polymer nanocomposites. This new composite, named as the mechanically interlocked interface polymer nanocomposite (^MIIPNC), has shown remarkable performance enhancements of 25.3-fold in strength and 431.3-fold in toughness. This exceptional mechanical enhancement is due to a highly crosslinked, rigid yet dynamically mobile interfacial architecture, that extends beyond conventional rotaxane sliding or hidden chain release mechanisms. On the one hand, mechanically interlocked [2]rotaxane-grafted nanoparticles act as high-density macro-crosslinks, effectively suppressing crack propagation with superior efficacy in releasing network tension near the crack front by rotaxane sliding dissipation. On the other hand, rotaxane-sliding-facilitated nanoparticle redistribution drives adaptive network reconfiguration, weakening the network disruption under large deformation. The incorporation of mechanical interlocking interfaces into polymer nanocomposites can unlock simultaneous high strength, toughness, and elongation at break. This strategy, which simultaneously leverages the dynamic supramolecular mobility and the reinforcement effect of rigid nanoparticles, establishes a versatile platform for designing ultra-tough, high-strength nanocomposites.