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

Abstract

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 polyurethane (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 (2.86 × 10‐6 S/cm), high transparency (average transmittance > 89%, 400~800 nm), excellent mechanical properties (tensile strength of 3.06 MPa, elongation at break of 1760%, and fracture energy of 14.98 kJ/m2), appreciable self‐healing 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 micro‐expression changes. This study provides a simple and effective strategy for the development of flexible and soft ionic conductors for sensors and human‐machine interfaces.

Solid-state, liquid-free ion-conducting elastomers: rising-star platforms for flexible intelligent devices

“…30–33 Owing to their unique features, circumventing the use of a liquid phase in soft ionic conductors, solid-state, liquid-free, ion-conducting elastomers possess excellent anti-freezing and anti-evaporating capacities in a wide temperature range, and are also capable of withstanding liquid leakage upon exposure to various external mechanical stimuli, thus maintaining long-term stable performances. 34–38 As expected, great progress has been realized in the area of solid-state, liquid-free ion-conducting elastomers ranging from their design and manufacturing to applications (Fig. 2); however, a comprehensive review on this emerging topic is still missing to date.…”

Liquid-free ionic conductive elastomers with high mechanical properties and ionic conductivity for multifunctional sensors and triboelectric nanogenerators

“…39 Based on the synergy of reversible dynamic disulfide bonds and hydrogen bond interactions, Yang et al introduced a polyurethane-based ionic conductor with a mechanical strength of 3.06 MPa, an ionic conductivity of 2.86 × 10 −3 mS cm −1 , and a healing efficiency of >90% using polydimethylsiloxane as a soft-chain segment. 40 Wang et al reported a polyurethane-based ionic conductor based on reversible imine dynamic crosslinking with a mechanical strength of 0.24 MPa, an ionic conductivity of 0.204 mS cm −1 , and a healing efficiency of 96%. 41 Although effective progress has been made toward the healing and reprocessing abilities of polyurethane-based ionic conductors, 17,27,42 achieving simultaneous enhancement of their mechanical properties and electrical conductivity is difficult.…”