Fabrication of Strong, Water‐Resistant, and Multifunctional Soy Protein Adhesives With Excellent Initial Adhesion Inspired by Sandcastle Worms

ABSTRACT The development of soy protein (SP) adhesives that exhibit high bonding strength, water resistance, and initial adhesion remains a significant challenge. Herein, inspired by sandcastle worms, a strong, water‐resistant, and multifunctional SP adhesive with excellent initial adhesion is fabricated by introducing graft‐modified quaternized kraft lignin (QKL) and poly‐γ‐glutamic acid (PGA) into the SP matrix to construct supramolecular networks. The rigid skeletal framework of QKL provides structural stability and the electrostatic interactions between PGA and QKL enhance crosslinking strength, leading to a 5.5‐fold increase in adhesion strength to 1.43 MPa relative to unmodified SP. Furthermore, the ester bonds formed after hot pressing and the rigid QKL synergistically enhance the cohesion force of the adhesive, resulting in a 3.2‐fold increase in bonding strength to 3.71 MPa compared to unmodified SP. Additionally, the polyaromatic groups of QKL and the dense covalent crosslinks in the adhesive promote the formation of hydrophobic structures that inhibit water invasion, achieving a 4.5‐fold increase in wet bonding strength to 1.86 MPa versus unmodified SP. Meanwhile, the adhesive also exhibits outstanding toughness, flame retardancy, mildew resistance, and antibacterial properties. This biomimetic strategy offers an efficient method for fabricating strong, water‐resistant, and multifunctional biobased adhesives with exceptional initial adhesion.