Recyclable, Highly Thermally Stable and Intrinsically Flame Retardant Bio‐Based Polybenzoxazine Vitrimers Enabled by Dual Dynamic Covalent Bonds

Vitrimers represent an emerging class of polymeric materials that combine mechanical robustness and dimensional stability while still maintaining reprocessability and degradability. Despite considerable advances in studies of vitrimers, there remains a pressing demand for developing robust dynamic covalent chemistries that enable the vitrimers with high thermal stability and intrinsic flame retardancy. In this work, we design a dual dynamic covalent network in benzoxazines using bio-based precursors derived from vanillin and sustainable diamines, in which imine bonds and silyl ether bonds are strategically incorporated to break through the trade-off between degradability and high performance. Notably, the newly obtained polybenzoxazine vitrimers exhibit outstanding thermal stability (with a 10% weight loss temperature of 361.7°C and char yield of 61.4%), exceptional flame retardancy (V-0 ranking), and undergo complete degradation within 6 h under alkaline conditions. This study broadens the range of sustainable vitrimers and establishes a new design paradigm for reconciling the traditionally competing properties of recyclability, thermal robustness, and fire safety in thermosetting materials.