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

TLDR

Covalent cross‑linking gives rubbers resilience and durability but hinders healing and recycling, and existing dynamic covalent elastomers either require complex chemistry or exhibit weak mechanical properties. This study presents a simple method to create mechanically robust, healable, and recyclable elastomeric vitrimers by incorporating dual dynamic cross‑links of boronic esters and metal‑ligand coordination into commercial rubber. Epoxidized natural rubber is cross‑linked with a boronic‑ester dithiol cross‑linker, and the resulting network can rearrange through boronic‑ester transesterification while metal‑ligand coordination bonds provide additional sacrificial interactions. Introducing sacrificial metal‑ligand coordination bonds markedly improves the mechanical strength while preserving healing and reprocessability.

Abstract

Covalent cross-linking of rubbers is essential for obtaining high resilience and environmental resistance but prevents healing and recycling. Integrating dynamic covalent bonds into cross-linked rubbers can resolve the trade-off between permanent cross-linking and plasticity. The state-of-the-art elastomer-based dynamic covalent networks require either intricate molecular makeup or present poor mechanical properties. In this work, we demonstrate a simple way to prepare mechanically robust yet healable and recyclable elastomeric vitrimers by engineering dynamic dual cross-links of boronic esters and coordination bonds into a commercial rubber. Specifically, epoxidized natural rubber is covalently cross-linked with a boronic ester cross-linker carrying dithiol through chemical reaction between epoxy and thiol groups. The covalently cross-linked networks are able to alter the topologies through boronic ester transesterifications, thereby conferring them with healing ability and reprocessability. In particular, the mechanical properties can be remarkably enhanced by introducing sacrificial metal–ligand coordination bonds into the networks without compromising the healing ability or reprocessability.