Bioinspired Polymers Get Sticky On Demand

Drawing inspiration from the sticky adhesive proteins produced by mussels and sandcastle worms, a multidisciplinary research team has devised a synthetic pathway to make adhesive polymers for underwater applications without the polymers getting fouled up during processing (J. Am. Chem. Soc., DOI: 10.1021/ja309044z). Chemists have tried to use the dihydroxy functional group of catechols to mimic the amino acid 3,4-dihydroxy-l-phenylalanine, which gives marine adhesive proteins their stickiness. But the catechols are susceptible to oxidation, side reactions, and untimely adhesion that diminish polymer performance. Craig J. Hawker of the University of California, Santa Barbara, and his colleagues overcame these problems by using silyl groups to protect the hydroxyl groups. The researchers added triethylsilyl groups to eugenol, a natural catechol found in clove oil, then coupled protected eugenol to thiols along the backbone of a commercially available polysiloxane. After using lithographic techniques to make patterned polymer substrates, they removed the silyl groups with a mild acid to unveil the sticky surface. The technique should provide a versatile platform for underwater and biomedical applications, Hawker says, including adhesive coatings, antifouling surfaces, and bone glues.