Self-Healing Alkyl Acrylate-Based Supramolecular Elastomers Cross-Linked via Host–Guest Interactions

Abstract

We prepared acrylamide monomers with permethylated cyclodextrins (PM-CDAAmMe) or peracetylated cyclodextrins (PAc-CDAAmMe). PM-CDAAmMe and PAc-CDAAmMe are soluble in various hydrophobic liquid acrylate monomers, and they can form inclusion complexes with guest monomers such as adamantane or fluoroalkyl groups tethered to a vinyl residue. The bulk polymerization of the liquid acrylate monomers with the PM-CDAAmMe or PAc-CDAAmMe monomers and the guest monomers gave highly flexible and tough elastomers. Tensile tests on the obtained supramolecular elastomers showed fracture strains of over 800% and fracture energies that were 12 times larger than those of covalently cross-linked conventional elastomers, indicating that the host–guest cross-linking made the supramolecular elastomers quite tough. During the deformation process, the applied stress is dispersed into the supramolecular elastomers by dissociation and recombination of the reversible host–guest complex. Moreover, these host–guest complexes also allow the adhesion of fractured pieces of the supramolecular elastomers without adhesives. The mechanical strength of the fractured elastomer was restored to ∼99% of its initial strength within 4 h. The self-healing properties can be attributed to the reversible cross-linking by the host–guest interactions.