Macromolecules, Vol.52, No.7, 2659-2668, 2019
Self-Healing Alkyl Acrylate-Based Supramolecular Elastomers Cross-Linked via Host-Guest Interactions
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 similar 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.