Mechanoresponsive Healable Metallosupramolecular Polymers

The development of polymers that possess superb mechanical properties and at the same time are capable of sensing damage and self-healing is presented. Copper-catalyzed azide-alkyne cycloaddition (CuAAC) based tridentate ligand 2,6-bis(1,2,3-triazol-4-yl)pyridine (BTP) and covalent mechanophore spiropyran (SP) units are incorporated into the polymer backbone to prepare ligand macromolecule. Upon coordinating with transition or lanthanide metal salts, metallosupramolecular films with phased-separated soft/hard morphology are spontaneously formed. The resulting materials show a rare combination of strong, tough, and elastic mechanical properties and are able to sense damage by changing optical properties. The Zn2+-containing material can self-heal in the presence of solvent and fully restore its mechanical properties. The underlying structure-property relationship is unveiled. In particular, the interplay between the covalent SP mechanophore and the noncovalent metal-ligand interactions and their hard phase is demonstrated.