Bio-derived Schiff base vitrimer with outstanding flame retardancy, toughness, antibacterial, dielectric and recycling properties

Thermosetting resins are widely used in high-tech applications for excellent mechanical robustness and chemical resistance. With increasing attention to the environmental and usage safety issues, it is necessary to develop bio-derived, recyclable, tough, and fire-retardant thermosetting resins. Herein, a high-performance, vanillin-based vitrimer (CIP_1.0) was prepared. The CIP_1.0 with 1.0 wt% phosphorus passes vertical burning (UL-94) V-0 rating with a limiting oxygen index (LOI) of 27.2%. The phosphorus-containing and Schiff base groups act synergistically in gas and condensed phases during combustion, endowing CIP_1.0 with outstanding fire retardancy. The CIP_1.0 shows excellent toughness with high elongation at break of 45.0% due to the π-π stacking of numerous rigid aromatic groups and appropriate cross-linking density. The highly symmetrical structure and low polarizability of CIP_1.0 result in a low dielectric constant. The CIP_1.0 exhibits superior antimicrobial properties. The CIP_1.0 can be reprocessed by hot-pressing at 140 °C for 10 min. The non-destructive, closed-loop recycling of carbon fibers in the carbon fiber-reinforced CIP_1.0 composite can be achieved under mild conditions due to the degradable Schiff base groups of CIP_1.0. In this work, a bio-derived, tough, fire-retardant, low dielectric, and antimicrobial vitrimer is prepared to provide a rational strategy for the design of advanced environmentally friendly thermosetting resins.