Effective enhancement of mechanical properties in protic ionic liquid-based ionogels via doubly ionic hydrogen bonds

The inherent trade-off between structural flexibility and mechanical robustness, along with difficulties with long-term environmental compatibility, severely limits the practical use of ionogels in flexible electronics. To address these limitations, we present the design of doubly ionic hydrogen bond networks and the fabrication of highly tough ionogels. These strong physical interactions are engineered by integrating poly(acrylic acid) (PAA) with a protic ionic liquid (PIL) synthesized from 1,8-diazabicyclo[5.4.0]undec-7-ene and 1,2,4-triazole. Governed by hydrogen bonds and ionic interactions, the optimized ionogel achieves remarkable mechanical performance, exhibiting a maximum tensile strength of 24.30 MPa, a fracture strain of 480%, and an exceptional toughness of 93.95 MJ·m^-3. Moreover, the ionogel demonstrates excellent anti-drying and solvent-dependent swelling behavior, as well as thermal tolerance and strong adhesion. As a flexible strain sensor, the ionogel exhibits high sensitivity and excellent electrical signal stability, enabling the reliable capture of human motion signals. The work establishes a promising strategy for fabricating mechanically robust ionogels via creating doubly ionic hydrogen bond networks. It also provides new insights for advanced flexible sensors adaptable to dry and harsh working conditions.