Facile strategy of mussel-inspired polymer as a high-performance dry/ wet adhesive

Mussel-inspired polymers have attracted interest due to their strong adhesion to various substrates; however, the existing synthetic methods are usually complicated and require the utilization of organic solvents. In this work, a novel mussel-inspired polyamide amine-dihydrocaffeic acid (PPCA) polymeric adhesive was designed by grafting a catechol-containing dihydrocaffeic acid (DHCA) monomer to the polyamide amine (PPC) backbone as an economic commercial agent. Due to interactions between catechol groups and various substrate surfaces, PPCA can be used as a general-purpose adhesive for various substrates and exhibited excellent adhesion to low-energy hydrophobic surfaces (e.g., an adhesive strength of 0.35 +/- 0.02 MPa for PTFE). No tedious solidification processes were required to reduce the energy and time consumption of the process while exhibiting long-term adhesion. Epichlorohydrin (EPI) was integrated into the polymer system to generate self-crosslinking to improve the cohesive strength, which further improved its adhesive performance. This adhesive also exhibited excellent wet adhesion because the catechol groups induced synergistic electrostatic and hydrogen-bonding interactions between azetidinium groups and phenols. This facile strategy provides a clean and general method to prepare strong adhesives for structural engineering applications under harsh conditions.