Closed‑Loop Recyclable Water‑Triggered Debond‑on‑Demand Polybenzoxazine Adhesives Enabled by Orthogonal Covalent Adaptable Networks

Advanced manufacturing requires debond-on-demand (DoD) adhesives that combine strong service adhesion with facile end-of-life disassembly and closed-loop recyclability, yet high adhesion often compromises clean debonding. Herein, we report a mild, scalable, and sustainable route to a water-debondable covalent adaptable network (CAN) adhesive containing orthogonal imine/amine and silyl ether/silanol dynamic covalent linkages, prepared by copolymerizing vanillin-based silyl ether benzoxazine (VBZ) with branched polyethyleneimine (bP). Relative to an imine-deficient guaiacol-based control, the copolymer displays a high glass-transition temperature (70 °C), superior creep recovery, and a fourfold reduction in stress-relaxation activation energy (31 kJ·mol−1), highlighting the key role of imine-mediated bond-exchange kinetics. The adhesive exhibited high lap shear strength (∼8 MPa) and load-bearing capacity (∼100 kg), while complete water-triggered debonding (80 °C, 30 min) enabled clean substrate recovery and reuse. The reclaimed resin was recyclable and reprocessable and retained mechanical properties comparable to the pristine material.