Mussel-mimetic self-healing polyaspartamide derivative gel via boron-catechol interactions

The catechol group from catechol of 3,4-dihydroxyphenethylamine (DOP, dopamine) has the ability to interact with metal ions to form non-covalent bonds in polymer chains. In this study, a novel kind of mussel-inspired copolymer, dopamine-conjugated poly(hydroxyethyl aspartamide), polyAspAm(DOP/EA), was synthesized and its interaction with boric acid (H3BO3) to form a cross-linked gel via boron-catechol coordinative binding was investigated. The copolymer was designed to contain a pH responsive adhesive catechol group, which reversibly underwent gelation through the metal-catechol binding, as proved by UV-Vis spectroscopy. When the pH is increased from acidic conditions to a specified pH (pH > 9), the B(OH)(3) is considered to have a functionality of two to bind catechols, leading to bis-complexes. In addition, the reversibility of the boron-catechol bonds provides self-healing characteristics to the polyAspAm gels. The rheological results showed that boron-catechol coordination could lead to quick and full recovery after the fracture of a gel specimen. This novel pH-responsive and self-healing gel system has potential in various applications including smart hydrogels, medical adhesives, and sealants.