High-performance benzoxazines designed with disulfide-imine networks

To address the challenges of limited degradation of benzoxazine resins, incorporating reversible covalent bonds into their crosslinked network offer a promising solution. However, a single dynamic bond often fails to provide sufficient dynamic properties. In this study, we introduce two distinct dynamic covalent bonds-imine and disulfide-into vanillin-derived benzoxazine resins to enhance their dynamic characteristics. These resins exhibit significantly reduced stress relaxation times (140 °C, 30 s), robust post-processing capabilities (140 °C, 10 MPa, 20 min), excellent thermal stability (54.4% char yield at 800 °C), and superior degradability compared to conventional benzoxazine counterparts. While a single dynamic bond (S-S or C=N) enables resin degradation within 24 h, the dual dynamic bond system achieves complete dissolution in just 16 h. The study reveals that initial dissociation of the S-S bond reduces the cross-link density of PVf-4AFD, facilitating the dissociation of C=N bonds. This synergy, while preserving the material's mechanical and thermal properties, accelerates the degradation process. This work advances the development of sustainable thermoset polymers by establishing a bi-dynamic crosslinked network, effectively balancing degradation rate, storage modulus, and thermal properties. The approach enables efficient reprocessing without compromising performance, providing a versatile strategy for designing degradable and recyclable benzoxazine resins. • Imine and disulfide bonds are added to enhance the dynamics of benzoxazines. • Synthesized benzoxazines show a stress relaxation time of 30 s at 140 °C. • Dual dynamic bonds enable full dissolution of the network within 16 hours. • Recycled carbon fibers retain 97.3% of their tensile strength after reuse.