Modification of Cork with Deep Eutectic Solvent and Dopamine for Enhanced Soy Protein-Based Wood Adhesives

Natural plant cells featuring polygonal honeycomb architectures exhibit exceptional load-bearing and energy dissipation capacities. The strategic incorporation of this biomimetic structure presents an effective reinforcement approach for composite materials. In this study, a fully biobased and sustainable soy protein adhesive with improved water resistance and bonding strength was developed through the integration of modified cork. The cork was modified via a two-step process: deep eutectic solvent treatment to partially remove lignin while preserving the unique cellular framework, followed by dopamine hydrochloride functionalization to improve interfacial reactivity and promote extensive hydrogen bonding with the soy protein matrix. The resulting composite adhesive demonstrated remarkable improvements in performance, achieving a wet shear strength of 1.15 MPa and a 111.8% increase in fracture toughness compared with unmodified soy protein adhesive. This work provides an effective strategy for fabricating high-performance, fully biobased adhesives and highlights the value-added utilization of cork as a functional reinforcement material.