Rapid preparation of high strength, high stretchability, transparent, self-healing conductive elastomers for strain sensors by photo-initiated copolymerization of two novel polymerizable deep eutectic solvents

Deep eutectic ionic conductive elastomer (DEICE) has become the focus of the development of new flexible ionic conductors due to its green and efficient preparation process and excellent electrical properties, which has been widely used in wearable devices, nanogenerators, 3D printing and other hot fields. However, due to the limitations of the existing polymerizable deep eutectic solvents (PDES) types, it is still challenging to rapidly prepare DEICE with excellent tensile properties and strength. In this study, we prepared DEICE by rapid in-situ photoinitiated copolymerization of two novel PDES: 2-carboxyethyl acrylate (CEA)/Choline chloride (ChCl) and N-(2-Hydroxyethyl)acrylamide (HEAA)/ChCl. The CEA-type PDES constitutes a soft segment, and the HEAA-type PDES constitutes a hard segment. It was found that the DEICE with a ratio of CEA type PDES to HEAA type PDES of 1:1 (monomer mass ratio) exhibits both excellent fracture strength and stretchability (5.08 MPa, 1050 %) due to the appropriate strong hydrogen bond crosslinking of the hard segment and the chain entanglement of the soft segment. In addition, the elastomer also has excellent optical properties (average transmittance of visible light >90 %), good conductivity (6.42 × 10−4 S/m), self-healing ability, high sensitivity (GF = 2.22), excellent linearity sensing ability (R2 = 0.999) and self-healing sensing ability. The sensor constructed by the elastomer can recognize human motions of various fineness, which proves its potential as a wearable device. Finally, the two new types of PDES proposed in this work also greatly broaden the existing PDES types, which provides the possibility for the future preparation research of DEICE with higher performance.