Halogen-Atom-Substituted DOPA with Enhanced Wet Adhesion and Antioxidization Ability

3,4-Dihydroxyphenylalanine (DOPA) has inspired the development of artificial adhesives, but efforts to enhance its adhesion strength and durability continue to evolve. However, it is tough work to improve DOPA wet adhesion by chemically decorating DOPA itself, despite the potential benefit of a concise and high-quality adhesion unit. Here, we synthesized a series of DOPA substituents by introducing different electron-withdrawing groups at the ortho position of the phenyl ring. This modification allowed us to effectively control the adhesion and antioxidation properties of DOPA. Combining atomic force microscopy (AFM)-based single-molecule force spectroscopy (SFMS) and cyclic voltammetry, we comprehensively investigated DOPA's antioxidation and adhesion capabilities. We found that adding a chlorine or bromine atom to the catechol ring significantly increases the DOPA wet adhesion strength. Additionally, halogen-substituted DOPA exhibited greater stability than dopamine in liquid solutions. Notably, chlorine-substituted DOPA maintained a strong adhesion ability even in salt water, offering potential benefits for bioadhesive applications.