Toughening Eutectic Gels by Lewis Acid-Induced Salting-Out

Eutectic gels are generally regarded as mechanically weak due to the plasticizing effect of deep eutectic solvents, which limit their application under mechanically demanding conditions. Here, we demonstrate that Lewis acids can trigger salting-out behavior, a mechanism well established in aqueous systems but largely unexplored in nonaqueous media, to markedly enhance the performance of eutectic gels. Experimental and computational analyses reveal that Lewis acids competitively coordinate with both eutectic solvent molecules and polymer networks. They either bind to the solvent molecules and displace them from the polymer, or directly coordinate with the polymer due to their stronger binding affinity. This coordination suppresses solvent-induced plasticization and promotes chain-aggregation-driven phase separation. As a result, the eutectic gels exhibit significantly improved mechanical properties, including a fracture stress of 12 MPa, a Young's modulus of 52 MPa, and a fracture energy of 41 kJ m–2, representing 17, 288, and 11-fold enhancements over their untoughened counterparts. The toughened gels also display robust tissue adhesion and broad damping capability, enabling use as wearable bioelectrodes that effectively reduce motion artifacts during electromyography and electrocardiography monitoring. This work unveils a previously unrecognized toughening mechanism in nonaqueous eutectic systems, advancing the design of high-performance functional soft materials.