High-performance benzoxazines designed with disulfide-imine networks

Abstract

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 CN) 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 CN 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.