Mechanically robust thermosets featuring room-temperature repairability and chemical upcyclability

Abstract

Conventional thermosets cannot self-repair at room temperature due to their immobilized networks and chain segments in the glassy state and are unrecyclable due to permanent cross-links. Herein, we design a new class of room-temperature self-healing thermosets with chemical upcyclability. The incorporation of amine-terminated dangling chains into the cross-linked networks provides two complementary advantages: (i) the terminal amines readily form hydrogen bonds with hydroxyl and ester groups, and due to their high mobility, these hydrogen bonds can reorganize in the glassy state; (ii) the hydrogen-bond network mediated by terminal amines effectively weakens the bond energy of disulfide bonds, thereby facilitating their dynamic exchange under mild pressure at room temperature. ¹³C NMR of the soluble network fraction together with gel-fraction analysis indicates that tertiary-amine-assisted transesterification may occur to a limited extent under mild pressure at room temperature. Consequently, the cross-linked networks exhibit exceptional room-temperature self-healing capability. Remarkably, the damaged material autonomously restores 86.8% of its tensile strength at room temperature without external intervention and achieves 100% recovery within 30 min under mild pressure. Moreover, end-of-life ETs can be mildly degraded and efficiently chemically upcycled into high-performance poly(urethane-urea) elastomers. This work presents a practical molecular strategy for sustainable thermosets that couple glassy-state self-repair with mechanical robustness and circular-economy compatibility.