Facile Preparation of Lignin-Based Underwater Adhesives with Improved Performances

Bioinspired wet adhesives have demonstrated versatile applicability in humid conditions, but the attainment of catecholic protein mimics comprises multistep synthesis and use of complex chemical components. Advanced wet adhesives derived from inexpensive bioresources and green processing are highly expected. We report a straightforward means to underwater-implemented adhesives from aqueous mixing of lignosulfonate (LS) and a polyamidoamine-epichlorohydrin (PAE-Cl) solution. The formation of a fluidic LS-PAE complex was driven by a delicate balance between electrostatic attraction and hydrophilic stabilization. The obtained adhesive highlights instant wet adhesion on diverse submerged surfaces and spontaneous curing in water. More importantly, it demonstrates robust and stable bonding strength over the alkali, salty, high-temperature, and long-time soaking conditions. This work advanced the development of lignin into functional wet adhesives through a green and sustainable approach.