Strengthening and Toughening Dynamic Covalent Thermosets via Hydrogen-Bonded Cross-Links

Dynamic covalent thermosets have emerged as a next-generation sustainable plastic that combines the advantages of traditional thermosets and thermoplastics. However, dynamic covalent thermosets generally suffer from the trade-off between strength/stiffness and ductility/toughness. Herein, a strategy to simultaneously strengthen and toughen dynamic covalent thermosets, incorporation of hydrogen-bonded (H-bonded) cross-links into the dynamic covalent networks, is reported. We designed a polyimine network cross-linked by both the dynamic imine bonds and H-bonds, resulting in a remalleable and recyclable polyimine thermoset with high yield strength (ca. 55.2 MPa) and Young's modulus (ca. 1.7 GPa) as well as high ductility (ca. 72%) and toughness (ca. 32.7 MJ m–3). When the H-bonded cross-links are removed from the polyimine network or replaced by the imine bonds, the mechanical strength or toughness of the polyimines is significantly declined, respectively. Therefore, this work provides an effective design principle for strong and tough dynamic covalent thermosets with modularity and recyclability.