Mechanically robust, fast self-healing epoxy vitrimers based on TBD catalyzed dynamic imine and siloxane exchanges

Epoxy vitrimers represent an important kind of self-healing and reprocessable resins. However, developing epoxy vitrimers with both high mechanical strength and fast self-healing properties at mild temperatures is a challenging endeavor. Herein, the 1,5,7-triazabicyclo [4,4,0]dec-5-ene (TBD) catalyzed imine and siloxane exchange approach is employed to tackle problem. A novel curing agent (APDI) containing imine and siloxane bonds was synthesized and used to prepare a double dynamically crosslinked epoxy vitrimer. The resultant epoxy vitrimer exhibit rapid stress relaxation characteristics (relaxation time 384 s at 100 °C) and fast repairing rate under mild thermal conditions (10 min at 90 °C). In addition, the epoxy resin vitrimer showed a tensile strength of up to 43.75 MPa and a high service temperature (a glass temperature of 78.1 °C and an initial degradation temperature of 331 °C). Furthermore, by incorporation of Fe₃O₄ nanoparticles into the epoxy vitrimer matrix, the epoxy vitrimer demonstrated fast (5 min) near-infrared light crack-healing ability. The fast self-healing mechanism was revealed to involve TBD acting as a shuttle catalyst, facilitating the synergistic exchange reaction of imine and siloxane bonds at the molecular level. Hydrolysis of imine linkages can be efficiently achieved under mild acid conditions, demonstrating its environmental sustainability. Hence, the novel approach of the creating of epoxy vitrimers possessing both high mechanical properties and fast self-healing properties at mild temperatures will enlighten future vitrimer material design and functional applications.