Fabrication of Polyurea-Based Ionogels for Strain Sensing with High Conductivity, Flame Retardancy, and Room-Temperature Self-Healing

Flexible sensors used under high temperatures and open flames are in high demand in fire rescue and similar scenarios, yet related research remains limited. An intrinsic flame-retardant polyurea-based ionogel with high ionic conductivity and room-temperature self-healing ability is developed in this work. Reactive ionic liquid (IL) containing phosphorus/nitrogen (P/N) flame-retardant groups and dynamic disulfide bonds is covalently incorporated into the polyurea backbone as a chain extender, constructing a dynamic network. The ionic conductivity of the ionogel is as high as 0.169 S/m, with a tensile strength of 2.2 MPa and an elongation at break of 1027%. Meanwhile, 99.5% of the tensile strength is recovered at room temperature after 24 h of self-healing. The polyurea-based ionogel containing P/N groups is intrinsically flame retardant, as evidenced by a limiting oxygen index of 28.8%, a UL-94 V-0 rating, and significantly suppressed heat and smoke release. The flexible strain sensor monitors human motions, even under high temperatures or fire exposure. This work provides a solution for the applications of intelligent sensing devices for fire rescue under high-risk conditions.