Ligand‐Controlled Coordination in Metal‐Salt Deep Eutectic Solvents for Regulating Phase Behavior, Network Connectivity, and Mechanical Performance of Stretchable Eutectogels

DES‐based eutectogels suffer from limited mechanical performance due to solvent‐induced plasticization, and phase separation alone cannot reliably reinforce network structures. Although metal‐salt‐based DESs enable coordination reinforcement, how ligand identity regulates coordination environment, phase behavior, and interdomain connectivity remains unclear. Here, we show that ligand‐controlled coordination dictates both network formation and phase behavior in intrinsically phase‐separating eutectogels. Using poly(N‐isopropylacrylamide) (PNIPA) and ZnCl 2 ‐based DESs with acetamide (AcAm) and ethylene glycol (EG) as ligands of distinct coordination strength, two regimes are identified. In PNIPA/ZnCl 2 –AcAm, weak Zn 2+ –AcAm coordination enables Zn 2+ bridging between polymer chains, suppressing phase separation and forming a homogeneous network with uniform polymer–Zn 2+ interactions, high transparency (> 90%), high elongation (2553%), and tensile strength of 5.21 MPa. In contrast, PNIPA/ZnCl 2 –EG shows strong Zn 2+ –EG coordination, limiting polymer–metal interactions and inducing coordination‐stabilized phase‐separated domains with reduced transparency (~50%), higher strength (14.45 MPa), and limited elongation (85%). Non‐coordinating choline chloride DESs yield weak networks (< 1.3 MPa), confirming that coordination‐governed connectivity dominates reinforcement. A mixed‐ligand system ([AcAm]/[EG] = 1:2) achieves balanced strength (7.67 MPa) and elongation (1270%). These results establish ligand‐controlled coordination as a general strategy to regulate phase separation and interdomain connectivity, enabling simultaneous optimization of strength and stretchability.