Covalent Adaptable Poly[2]rotaxane Networks via Dynamic C-N Bond Transalkylation.

Covalent adaptable networks (CANs), a novel class of crosslinked polymers with dynamic covalent bonds, have gained significant attention for combining the durability of thermosets with the reprocessability of thermoplastics, making them promising for emerging applications. Here, we report the first example of poly[2]rotaxane-type covalent adaptable networks (CANs), in which oligo[2]rotaxane backbones characterized by densely packed mechanical bonds, are cross-linked through dynamic C-N bonds. The oligo[2]rotaxane backbones could guarantee the mechanical properties of the CANs. Under an external force, the synergy of numerous microscopic motions of the cascade [2]rotaxane units, progressively introducing the initially hidden short chains, expands the polymer network, imparting good stretchability to the CANs (217 %). On the other hand, the dissociation of host-guest recognition, followed by the motion of mechanical bonds, constitutes a unique energy dissipation pathway, ultimately enhancing the toughness of CANs (7.6 MJ/m). In contrast, the control CAN, which lacks movable mechanical bonds, demonstrates significantly lower stretchability (40 %) and toughness (1.5 MJ/m). Moreover, the dynamic C-N bond can undergo high efficiency of 1,2,3-triazole alkylation and trans-N-alkylation exchanges at 1,2,3-triazolium sites at elevated temperatures, with good reprocessability and without compromising their mechanical performance. This work demonstrates the great potential of oligo[2]rotaxanes as a novel polymer backbone for the development of sustainable materials with excellent mechanical properties.