Tough and stretchable copolymer eutectogels constructed via in situ phase separation for flexible strain sensors

Abstract Deep eutectic solvent (DES)‐based eutectogels, known for their superior ionic conductivity, non‐volatility, biocompatibility, and cost‐effectiveness, have emerged as promising materials for flexible devices. However, the development of tough and stretchable eutectogels remains a significant challenge. Herein, we introduce a one‐step in‐situ phase separation strategy to fabricate tough and stretchable P(MAA‐ co ‐AAm)/TEAC‐EG copolymer eutectogels through random copolymerization of methacrylic acid (MAA) and acrylamide (AAm) in a tetraethylammonium chloride‐ethylene glycol (TEAC‐EG) DES. The poor compatibility of PAAm segments with TEAC‐EG DES results in the formation of a polymer‐rich phase, leading to energy dissipation during loading. Simultaneously, PMAA segments exhibiting good compatibility with DES, form a solvent‐rich phase that distributes stress and facilitates ion migration. The synergy between these two phases imparts ultratoughness and excellent conductivity to the copolymer eutectogel. The resultant copolymer eutectogel exhibits high strength (2.40 MPa), toughness (22.90 MJ m −3 ), and remarkable stretchability of 1340%, while demonstrating excellent self‐recovery, self‐healing abilities, and adhesive performance. Notably, its ionic conductivity reaches 1.07 mS cm −1 at 20°C, rendering these eutectogels well‐suited for applications as strain sensors in human motion detection. This study presents a facile approach to tune eutectogel microstructure and properties, thereby expanding their potential applications in high‐performance flexible electronics.