Strong, Reprocessable and Chemically Recyclable Biomass‐Derived Thermoset Materials Enabled by Dynamic Covalent Polybenzoxazine Networks

ABSTRACT Thermoset materials with high thermal stability and outstanding mechanical properties are widely utilized in high‐performance fields. However, the irreversible covalently crosslinking networks and highly dependent on petroleum‐based raw materials of conventional thermosets pose significant challenges for both recycling and sustainability. Herein, a series of dynamic ester bond‐containing benzoxazines have been synthesized using renewable resources. Specifically, the incorporated ester bonds enable the recyclability, while the abundant hydrogen bonding from the oxazine rings endows the polybenzoxazine networks with excellent thermal and mechanical properties. The resulting vitrimer, poly(BDO‐PA‐fa) , which is cured from the optimized benzoxazine monomer BDO‐PA‐fa , exhibits high thermal stability with a T g of 208°C and excellent reprocessability. Additionally, the carbon fiber reinforced polybenzoxazine composite ( CF/poly(BDO‐PA‐fa) ) fabricated from chemically degradable BDO‐PA‐fa is recyclable without fiber damage. CF/poly(BDO‐PA‐fa) shows exceptional mechanical and thermal performance with a tensile strength of 500.8 MPa, a flexural modulus of 33.3 GPa, and a T g of 220°C. Moreover, CF/poly(BDO‐PA‐fa) can be degraded under mild conditions, and the corresponding degradation products used as adhesives achieve a high adhesion strength of 2.17 MPa on iron substrates. This smart benzoxazine molecular engineering offers a versatile strategy for developing sustainable advanced thermoset materials with multiple recyclability using natural renewable biomass.