Mechanically Interlocked Vitrimers

Mechanically interlocked networks (MINs) have emerged as an encouraging platform for the development of mechanically robust yet adaptive materials. However, the difficulty in reversibly breaking the mechanical bonds poses a real challenge to MINs as customizable and sustainable materials. Herein, we couple the vitrimer chemistry with mechanically interlocked structures to generate a new class of MINs─referred to as mechanically interlocked vitrimers (MIVs)─to address the challenge. Specifically, we have prepared the acetoacetate-decorated [2]rotaxane that undergoes catalyst-free condensation reaction with two commercially available multiamine monomers to furnish MIVs. Compared with the control whose wheels are nonslidable under applied force, our MIVs with slidable mechanically interlocked motifs showcase enhanced mechanical performance including Young's modulus (18.5 ± 0.9 vs 1.0 ± 0.1 MPa), toughness (3.7 ± 0.1 vs 0.9 ± 0.1 MJ/m3), and damping capacity (98% vs 72%). The structural basis behind unique property profiles is demonstrated to be the force-induced host-guest dissociation and consequential intramolecular sliding of the wheels along the axles. The peculiar behaviors represent a consecutive energy dissipation mechanism, which provides a complement to other pathways that mainly depend on the breaking of sacrificial bonds. Moreover, by virtue of the vitrimer chemistry of vinylogous urethanes, we impart reprocessability and chemical recyclability to the MINs, thereby empowering the reconfiguration of the networks without breaking of the mechanical bonds. Finally, it is disclosed that the intramolecular motions of [2]rotaxanes could accelerate the dynamic exchange of the vinylogous urethane bonds via loosening the network, suggestive of a synergistic effect between the dual dynamic entities.