High-performance epoxy vitrimer with superior self-healing, shape-memory, flame retardancy, and antibacterial properties based on multifunctional curing agent

The lack of functionalities such as degradability, antibacterial, and flame retardancy is the key to limit the further wide application of conventional epoxy thermosets. In this work, a novel bio-based multifunctional amine curing agent (named HVPA), was successfully synthesized via the Schiff base reaction between six-vanillin functionalized cyclophosphazene and N-methylethylenediamine. And an epoxy vitrimer (HVPA/GDE) was fabricated by utilizing HVPA to cure the bio-based epoxy of glycerol diglycidyl ether (GDE). Ascribing to the even distribution of dynamic imine bond in each crosslinking linkage, this synthetic HVPA/GDE vitrimer presented excellent comprehensive properties including fast self-healing (8 min for 100%, without any pressure), excellent shape memory, easy reprocessability (1.5 MPa, 3 min, 100 °C), mild degradation, and superior bacterial resistance to both Gram-negative bacteria (E. coli) and Gram-positive bacteria (S. aureus). Moreover, due to the high content of N/P elements and benzene groups within the network structure, this HVPA/GDE not only exhibited excellent flame retardancy but also possessed good UV resistance and transparency, while maintaining comparable mechanical strength compared to the control group of commercial amine curing agent 4,4-Diaminodiphenyl methane (DDM) cured epoxy resin (DDM/GDE). Therefore, this work provides a facile strategy for fabricating multi-functional and high-performance bio-based epoxy resins.