Enhancing the Adhesion of a Biomimetic Polymer Yields Performance Rivaling Commercial Glues

Abstract

Marine mussels clinging to rocks inspire the development of novel materials. Characterization of mussel adhesive plaques describes a matrix of proteins containing 3,4‐dihydroxyphenylalanine (DOPA), which provides cross‐linking chemistry that allows mussels to attach firmly. Several synthetic polymer systems have been developed based on this DOPA chemistry. High strength bonding has been achieved with poly[(3,4‐dihydroxystyrene)‐ co ‐styrene], a simplified mimic of mussel proteins in which 3,4‐dihydroxystyrene provides the cross‐linking and adhesion of DOPA. The poly(styrene) host polymer stands in for a protein backbone. Prior efforts showed that a monomer ratio of 1:2 3,4‐dihydroxystyrene:styrene within the statistical copolymer poly[(3,4‐dihydroxystyrene)‐ co ‐styrene] yields the highest adhesion. To enhance adhesive performance of this biomimetic polymer, a systematic study is carried out in which a range of cross‐linking agents, cure times, cure temperatures, polymer concentrations, and fillers are examined. Lap shear adhesion testing revealed substantial increases in bond strength from each study. Consensus conditions are then determined and bonding performance is assessed on several substrates. Adhesion of this system turns out to be one of the strongest of all biomimetic polymers. These studies show that DOPA chemistry may be able to stand alongside of cyanoacrylate (e.g., Super Glue) and epoxy when it comes to high strength bonding.