Mechanically Robust, Self-Healable, and Reprocessable\nElastomers Enabled by Dynamic Dual Cross-Links

Abstract

Covalent\ncross-linking of rubbers is essential for obtaining high\nresilience and environmental resistance but prevents healing and recycling.\nIntegrating dynamic covalent bonds into cross-linked rubbers can resolve\nthe trade-off between permanent cross-linking and plasticity. The\nstate-of-the-art elastomer-based dynamic covalent networks require\neither intricate molecular makeup or present poor mechanical properties.\nIn this work, we demonstrate a simple way to prepare mechanically\nrobust yet healable and recyclable elastomeric vitrimers by engineering\ndynamic dual cross-links of boronic esters and coordination bonds\ninto a commercial rubber. Specifically, epoxidized natural rubber\nis covalently cross-linked with a boronic ester cross-linker carrying\ndithiol through chemical reaction between epoxy and thiol groups.\nThe covalently cross-linked networks are able to alter the topologies\nthrough boronic ester transesterifications, thereby conferring them\nwith healing ability and reprocessability. In particular, the mechanical\nproperties can be remarkably enhanced by introducing sacrificial metal–ligand\ncoordination bonds into the networks without compromising the healing\nability or reprocessability.