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

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.