Solvent-Free Mussel-Inspired Adhesive with Rapid Underwater Curing Capability

How to realize fast and strong underwater adhesion has gained much attention recently. Although some mussel-inspired adhesives that can be cured underwater have been reported, reports on underwater adhesion with both high bonding strength and rapid curing capability are still rare. Furthermore, organic solvents are generally utilized in these adhesives, which are eco-unfriendly. Here, by taking advantages of the strong underwater adhesion capability of catecholic groups in mussel adhesion proteins (MAPs) and the fast curing capability of polyurethane (PU) prepolymer, a facile yet powerful strategy towards a fast-curing mussel-inspired underwater adhesive is reported. The biomimetic adhesive, PUP-PPG-DBHP, is a liquid composed of isocyanate-terminated polypropylene glycol (PPG) and isocyanate-terminated dopamine bis(hydroxymethyl)propionate (DBHP), which can be directly applied underwater without solvent dilution and reach an average bonding strength around 1.2 MPa at a curing time of only around 30 s on glass substrates. Meanwhile, underwater curing process of PUP-PPG-DBHP shows good tolerance toward pH value, ionic strength, and temperature change. Such an engineering adhesive opens an innovative and facile route to a feasible solution for underwater engineering field.