Supramolecular Organic Nanofiller: A New Reinforcement Strategy for Dynamic Covalent Polymer Networks Toward Upcycling of Carbon Fiber Composites

Dynamic covalent polymer networks (DCPN) provide an important solution to the challenging recyclability of thermoset elastomers. However, dynamic bonds exhibit relatively weak bond energies, considerably decreasing the mechanical properties of DCPN. Herein, a novel reinforcement strategy for DCPN involving the in situ formation of supramolecular organic nanofillers through asynchronous polymerization is proposed. Owing to the difference in the reactivity of the isocyanate groups and the gradual deblocking of aldimine, asynchronous cross-linking of hexamethylene diisocyanate and isocyanate-terminated prepolymer containing dynamic oxime-urethane bonds with the deblocked tris(2-aminoethyl)amine facilitates the transition from the molecular interpenetration of chains into immiscible polymerization. This results in thermodynamic incompatibility between the hyperbranched clusters and long chains, inducing a spontaneous formation of supramolecular organic nanofillers. Compared to traditional reinforcement strategies, supramolecular organic nanofillers considerably improve the mechanical properties of DCPN. Furthermore, the supramolecular interactions between hyperbranched clusters and dynamic oxime-urethane bonds enable the network with excellent recyclability. The unique reinforcement and recyclability of the prepared DCPN allow their combination with carbon fibers (CF) to form CF composites with outstanding properties for personal-protection applications, achieving CF composite upcycling. This study offers a novel strategy on the reinforcement of DCPN and the upcycling of high-performance CF composites.