Fabrication of Unprecedented Fully Biobased Recyclable Underwater Adhesives with High Bonding Strength and Water Resistance via an Adhesion-Cohesion Balance of Bioinspired Catechol-Disulfide Bond Strategy

The fabrication of fully biobased adhesives is greatly significant for the green and sustainable development of the furniture, construction, and flooring industries. However, the poor bonding strength, water sensitivity, and mildew resistance seriously hinder their promotion and application. Herein, inspired by the structure of the catechol and disulfide bonds in mussel protein and hair protein, a fully recyclable underwater biobased adhesive with excellent bonding strength, water resistance, and exceptional antimildew performance is prepared. A balance is built between interfacial adhesive force and internal cohesive force via catechol interfacial adhesion of tannic acid (TA) and the dynamic disulfide thermal-responsive network between poly(lipoic acid) (LA) and soy protein (SP). Consequently, this biobased adhesive exhibits a remarkable improvement of bonding strength by 146.81% to 2.32 MPa compared to unmodified SP. Additionally, effective interfacial interactions and stable biomimetic hydrophobic cross-linking structures significantly enhance the water-resistant wet bonding strength by 306.45% to 1.26 MPa compared to unmodified SP. Moreover, the adhesive also possesses favorable underwater adhesion properties, mildew resistance, and recyclability. This biomimetic structural design provides a novel method for the fabrication of extraordinary-performance fully biobased adhesives.