Mussel-Inspired Self-Healing Double-Cross-Linked Hydrogels by Controlled Combination of Metal Coordination and Covalent Cross-Linking.

Mussel-inspired hydrogels held together by reversible catecholato-metal coordination bonds have recently drawn great attention owing to their attractive self-healing, viscoelastic and adhesive properties together with their pH-responsive nature. A major challenge in these systems is to orchestrate the degree of catechol oxidation that occurs under alkaline conditions in air and has a great impact on the aforementioned properties because it introduces irreversible covalent cross-links to the system, which stiffens the hydrogels but consume catechols needed for self-healing. Herein, we present a catechol-based hydrogel design that allows for the degree of oxidative covalent cross-linking to be controlled.

Mussel-Inspired Materials: Self-Healing through Coordination Chemistry.

Improved understanding of the underwater attachment strategy of the blue mussels and other marine organisms has inspired researchers to find new routes to advanced materials. Mussels use polyphenols, such as the catechol-containing amino acid 3,4-dihydroxyphenylalanine (DOPA), to attach to surfaces. Catechols and their analogues can undergo both oxidative covalent cross-linking under alkaline conditions and take part in coordination chemistry.

Metals & polymers in the mix: fine-tuning the mechanical properties & color of self-healing mussel-inspired hydrogels.

Reversible sacrificial bonds play a crucial role in various biological materials where they serve as load-bearing bonds, facilitating extensibility and/or impart self-healing properties to the biological materials. Recently, the coordination bonds found in blue mussel byssal threads have been mimicked in the design of self-healing hydrogels. Herein we show how the mechanical moduli of mussel-inspired hydrogels based on DOPA-polyallylamine (DOPA-PAA) can be straight-forwardly adjusted by systematically varying the coordinating metal from Al, Ga to In.

Self-healing mussel-inspired multi-pH-responsive hydrogels.

Self-healing hydrogels can be made using either reversible covalent cross-links or coordination chemistry bonds. Here we present a multi-pH-responsive system inspired by the chemistry of blue mussel adhesive proteins. By attaching DOPA to an amine-functionalized polymer, a multiresponsive system is formed upon reaction with iron.