Bioinspired design of elastomeric vitrimers with sacrificial metal-ligand interactions leading to supramechanical robustness and retentive malleability

Most elastomeric vitrimers suffer from mechanical weakness in practical applications. Inspired by the development of strong and tough biomaterials relying on sacrificial bond-detachment mechanisms, herein we describe the biomimetic design of elastomeric vitrimers with mechanical robustness, preservable malleability, and recyclability by engineering sacrificial metal-ligand coordination bonds into exchangeable networks. In particular, we use a commercially available metal complex, aluminum acetylacetonate (Al(acac)3), to catalyze cross-linking based on the silylation reaction between hydroxylated natural rubber and hydrosilanes, thus introducing dynamic silyl ether-based architectures into the rubber matrix. At the same time, the Al3+ ions can interact with the free oxygen-containing moieties on the rubber skeleton, enabling labile Al3+O coordination bonds in the covalent framework to substantially dissipate mechanical energy through reversible bond detachment/reattachment upon deformation. As the organic acetylacetonate ligands of Al(acac)3 can facilitate the dispersion of Al3+ ions in the matrix, incorporating a small amount of organometallic complex (0.68 wt% of elastomer matrix) achieves an unparalleled improvement of the strength, modulus, and toughness of the resulting vitrimers. Moreover, due to their temperature-dependent nature, the Al3+O coordination bonds will partially dissociate at elevated temperatures, which only slightly compromises the topological rearrangements of the silyl ether-based network, but barely affects the reprocessability.