Self-Healing Network Polymers Based on Dissociable [c2]Daisy-Chain Rotaxane Structures

To develop self-healing materials with mechanical strength, we designed a three-dimensional network polymer primarily composed of [c2]daisy-chain rotaxanes. Although polymeric materials incorporating [c2]daisy-chain rotaxanes have been reported, they all exhibit topological properties based on the non-dissociative nature of the rotaxane structure and do not undergo reversible host–guest association and dissociation. In this study, we designed a novel self-healing polymer that enables the reversible formation and dissociation of [c2]daisy-chain rotaxane. Specifically, a diacrylate containing a [c2]daisy-chain rotaxane was synthesized from a symmetrical Guest–Host–Guest (GHG) compound, in which two secondary ammonium salt units (Guests) were introduced into a single 24-membered dibenzo-crown ether (Host) unit. Subsequent Michael addition with a tetrafunctional thiol afforded a network polymer exhibiting reversible inclusion complex in response to various external stimuli. For example, under heating and cooling conditions, the gel underwent a gel-to-sol transition. In addition, the resulting organogel was readily remoldable after fracture and exhibited mechanical strength comparable to that before fracture. Furthermore, when the network polymer in either the dry or wet state was cut and the resulting surfaces were brought into contact, the fractured surfaces re-adhered. These results suggest the potential of this network polymer as a novel recyclable material.