Adhesion Promoting Copolymer of Acetate-Protected Vinyl Catechol with Glycidyl Methacrylate: Unraveling Deprotection, Adsorption, and Adhesion Behaviors on Metal Substrates

Epoxy resins are one of the important and intensively used thermosetting adhesives in the automotive and electronic industries. Understanding and improving the interfacial interactions between epoxy adhesives and metal adherends are essential and urgent issues that need to be overcome to expand the scope of adhesive applications. In this study, a bioinspired acetate-protected vinyl catechol (Ac2VCa) monomer derived from natural caffeic acid was copolymerized with glycidyl methacrylate (GMA) to prepare a catechol-containing polymer─PGMA-co-P(Ac2VCa)─for the enhancement of interfacial adhesion. The deprotection of acetate protecting groups using a diamine was validated, allowing the achievement of the deprotection and adsorption of the PGMA-co-P(Ac2VCa) promoter in one processing procedure for its direct usage as the primer or additive. With the incorporation of catechol moieties, the strengthened interfacial interactions can effectively improve the lap shear strength of epoxy-adhesive-bonded metallic joints.