Self-Healing and Creep-Resistant Injectable Hydrogel from Aminoborinate Chemistry and Phase Separation

Boronate-based hydrogels are of particular interest for diagnostics, drug-delivery, cell culture or 3D fabrication. The short lifetime of the reversible boronate cross-links makes them self-repairing and injectable. However, the high dynamics and low hydrolytic stability of boronates make it very difficult to produce hydrogels that behave like viscoelastic solids and exhibit stable properties. Here, we address these limitations by designing structured hydrogels incorporating aminoborinate cross-links. Using model studies, we demonstrate that aminoborinates undergo fast exchange reactions at room temperature and use this finding to prepare hydrogels by reacting a polyacrylamide bearing 1,2-amino alcohol functions with an aryl-rich bis-borinic cross-linker. The resulting cross-links aggregate into large hydrophobic domains, leading to structured hydrogels with a unique combination of solid-like behavior, injectability, autonomous self-healing ability, and long-term stability. Confining dynamic covalent cross-links within long-lived hydrophobic domains opens new avenues for designing injectable hydrogels with excellent chemical stability, tunable mechanical properties, and self-healing ability.