Mechanoresponsive Healable Metallosupramolecular Polymers

Abstract

The development of polymers that possess superb mechanical properties and at the same time are capable of sensing damage and self-healing is presented. Coppercatalyzed 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 Zn 2+ -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.

The btp [2,6-bis(1,2,3-triazol-4-yl)pyridine] binding motif: a new versatile terdentate ligand for supramolecular and coordination chemistry

“…117 Both of these systems involved polymeric poly-btp components. More recently, Weng and co-workers have also reported self-healing btp systems with stress-sensing abilities, 163 and PEG-linked systems, which formed multiresponsive gels both in the presence and absence of Eu(III). 164 We reported [Ru(4b) 2 ](PF 6 )Cl, the first example of a metal complex gelator derived from discrete mono-btp components, the X-ray crystal structure of which suggests that it is able to induce solvent gelation by the formation of supramolecular polymer chains through hydrogen bond interactions between the carboxylic groups, ethanol solvent molecules and chloride anions.…”

Intrinsic Self-Healing Polymers Based on Supramolecular Interactions: State of the Art and Future Directions

“…Gels swollen in acetonitrile or THF and crosslinked with Zn(OTf) 2 or Eu(OTf) 3 demonstrated excellent self-healing behavior. Another approach using CuAAC to copolymerize BIP and spiropyran (SP) in a polyurethane backbone was shown [197]. The addition of Zn 2+ or Eu 3+ leads to the formation of supramolecular gels revealing a hard/soft morphology.…”

Mechanochemical Reactions Reporting and Repairing Bond Scission in Polymers

“…Furthermore, if a sample was stretched, activating the spiropyrans, then irradiated with light whilst being held at constant strain to close the merocyanines, it was found that the spiropyrans opened once more after 1-2 h, demonstrating force-induced change in the energy landscape of the spiropyran-merocyanine transformation. Lastly, spiropyran has also been employed in combination with supramolecular cross-links, such as hydrogen-bonding dimers [15] and transition metal or lanthanide complexes [25], to create stress-reporting, self-healing gels.…”