Catechol-Amine-Decorated Epoxy Resin as an Underwater Adhesive: A Coacervate Concept Using a Liquid Marble Strategy

The attachment phenomena of various hierarchical architectures found in nature, especially underwater adhesion, have drawn extensive attention to the development of similar biomimicking adhesives. Marine organisms show spectacular adhesion characteristics because of their foot protein chemistry and the formation of an immiscible phase (coacervate) in water. Herein, we report a synthetic coacervate derived using a liquid marble route composed of catechol amine-modified diglycidyl ether of bisphenol A (EP) polymers wrapped by silica/PTFE powders. The adhesion promotion efficiency of catechol moieties is established by functionalizing EP with monofunctional amines (MFA) of 2-phenyl ethylamine and 3,4-dihydroxy phenylethylamine (DA). The curing activation of MFA-incorporated resin pointed toward a lower activation energy (50.1-52.1 kJ mol^-1) compared with the neat system (56.7-58 kJ mol^-1). The viscosity build-up and gelation are faster for the catechol-incorporated system, making it ideal for underwater bonding performance. The PTFE-based adhesive marble of the catechol-incorporated resin was stable and exhibited an adhesive strength of 7.5 MPa under underwater bonding conditions.