Tuning Hydrogel Mechanics Through Synergistic Metal-Ligand Coordination and Chemical Fueling

Abstract

Chemically fueled anhydride formation offers a powerful strategy to create polymer networks with transient mechanical reinforcement. In this work, metallo-supramolecular hydrogels were developed with two independent crosslinking mechanisms, metal-ligand coordination and transient anhydride formation, yielding materials capable of programmable stiffness, intrinsic self-healing, and temporally controllable properties. Bis(pyridin-2-ylmethyl)amine (DPA) units were incorporated into polymers as ligands. The coordination strength of the resulting persistent dynamic cross-links is tunable by varying both the metal ion (Fe2+ or Ni2+) and the nature of the ligands through substitution with chloro or methoxy groups. Carboxylic acid repeat units provide fuel-driven transient anhydride formation on treatment with carbodiimides. The resulting transient cross-links can be tuned by changing the carboxylic acid structure, affecting the lifetime of the transient state and its stiffness. Lap-shear-inspired healing tests show that the materials achieve more than 90% healing under fueled conditions within 15 h. Notably, the fuel-driven process accelerates healing resulting from the persistent dynamic metal-ligand coordination. This work demonstrates a versatile platform for soft materials with programmable mechanics and autonomous self-healing.