Preparation and properties of bio-based degradable polybenzoxazines containing dihydrazone-based dynamic bonds

Abstract

Benzoxazine resins are widely used in the aerospace and electronics industries due to their high thermal stability and mechanical performance. However, their reliance on petroleum-based precursors and permanent crosslinked networks hinders recyclability, thereby creating environmental challenges. Although existing methods to introduce degradable bonds can improve recyclability, they often compromise thermal performance. To address these issues, we adopted a “rigid conjugated dynamic dihydrazone bond + bio-based synergy” strategy and designed a bio-based benzoxazine resin by synthesizing dihydrazone-containing bisphenol monomers from bio-vanillin and hydrazine hydrate, followed by polymerization with furfurylamine. This strategy incorporated acid-labile dynamic bonds into the crosslinked network while preserving thermal stability. The resin exhibited a char yield of 59.5% at 800 °C, comparable to those of petroleum-based analogues. Moreover, the dynamic network enabled controlled degradation under three conditions: elevated temperature, acetone–water mixtures (2 : 8, v/v), and 0.1 M HCl at 50 °C. In carbon fiber composites, 96% of the original fiber strength (2.64 vs. 2.75 GPa) was retained after 24 hours of resin decomposition, with minimal surface damage. This work demonstrates a bio-based approach for balancing thermal performance and recyclability in thermosetting composites, providing a practical pathway toward sustainable high-performance materials.