Liquid-Free, Self-Repairable, Recyclable, and Highly Stretchable Colorless Solid Ionic Conductive Elastomers for Strain/Temperature Sensors

Solid-state ionic conductive elastomers (ICEs) can fundamentally overcome the disadvantages of hydrogels and ionogels (their liquid components tend to leak or evaporate), and are considered to be ideal materials for flexible ionic sensors. In this study, a liquid-free ionic polyurethane (PU) type conductive elastomer (ICE-2) was synthesized and studied. The PU type matrix with microphase separation endowed ICE-2 with excellent mechanical versatility. The disulfide bond exchange reaction in the hard phase and intermolecular hydrogen bonds contributed to damage repairing ability. ICE-2 exhibited good ionic conductivity (2.86x10(-6) S/cm), high transparency (average transmittance > 89%, 400 similar to 800 nm), excellent mechanical properties (tensile strength of 3.06 MPa, elongation at break of 1760%, and fracture energy of 14.98 kJ/m(2)), appreciable selfhealing ability (healing efficiency > 90%), satisfactory environmental stability, and outstanding recyclability. The sensor constructed by ICE-2 could not only realize the perception of temperature changes, but also accurately and sensitively detect various human activities, including joint movements and microexpression changes. This study provides a simple and effective strategy for the development of flexible and soft ionic conductors for sensors and human-machine interfaces.