Stiff and Fracture‐Resistant Ion Gels Enabled by Synergetic Physical Entanglement and Hydrogen Bonding

In this study, ion gels are developed that simultaneously exhibit exceptional stiffness and fracture resistance through the synergistic effects of physical entanglements and hydrogen bonding between polymer chains within an ionic liquid matrix. Through radical copolymerization conducted in an ionic liquid under extremely low initiator concentrations, ultrahigh molecular weight polymers in situ with nearly complete monomer conversion are successfully synthesized. This strategy enabled the one-pot synthesis of physically crosslinked polymer gels composed of abundant entanglements and hydrogen bonds between polymer chains. Notably, it is demonstrated that the synergy between physical entanglements arising from ultrahigh molecular weight polymer chains and noncovalent hydrogen bonding enables the simultaneous enhancement of mechanical properties that typically exhibit trade-off relationships, such as stiffness, toughness, and fracture resistance. Consequently, the synthesized ion gels exhibited outstanding mechanical performances, ranking among the best previously reported tough polymer gels, while maintaining a favorable balance between ionic conductivity and mechanical strength. These findings underscore the broader significance of the approach, indicating that the integration of physical entanglements and reversible interactions offers a generalized pathway to mechanically robust materials across various polymer systems.