A Dynamically Cross-Linked, Stretchable, Self-Healing, and Recyclable Polyurethane-Based Ionogel for Flexible Strain Sensors

Flexible ionic conductors, as the core materials for next-generation electronic devices, are widely applied in electronic skin, wearable health monitoring devices, and flexible sensors. However, integrating excellent mechanical properties, efficient self-healing, and recyclability into one material remains challenging. In this work, we synthesize a polyurethane featuring dynamic supramolecular interactions by combining quadruple hydrogen bonds in side chains with disulfide bonds. This polymer exhibits outstanding mechanical performance, with a tensile strength of 17.6 MPa, an elongation at break of 1716%, and a toughness of 154.66 MJ/m³. Subsequently, an ionic liquid ([EMIM][TFSI]) is introduced via solvent evaporation, yielding a high-performance ionogel that marries dynamic supramolecular networks with ionic conductivity. The resulting ionogel achieved a tensile strength of 1.26 MPa, an elongation of 2585%, a toughness of 20.45 MJ/m³, along with remarkable self-healing ability and full recyclability. Based on these attributes, the ionogel is further fabricated into a flexible strain sensor, which demonstrates reliable sensitivity and excellent cyclic stability. This work provides a material platform and design concept for developing highly reliable, practical, and multifunctional flexible electronic devices.