Eutectogel-based strain and temperature sensor with widely tunable mechanical properties regulated by copolymerization-induced phase separation and electrostatic interaction

Eutectogels are compelling materials for flexible sensor owing to their intrinsic excellent ionic conductivity, biocompatibility, low fabricating expense and non-volatility. However, the design and preparation of robust eutectogel-based sensors with tunable mechanical and adhesive properties remains a challenge. Herein, we reported a facile one-pot method to fabricate high-performance eutectogels by copolymerization of two monomers with distinct electrolyte properties, acrylic acid (AA) and 2-(dimethylamino)ethyl methacrylate (DMAEMA). The copolymerization of AA and DMAEMA in deep eutectic solvent (DES) composed of choline chloride and glycerol could induce macroscopic phase separation, endowing the as-prepared PAA-co-PDMAEMA eutectogels with enhanced mechanical properties. By simply varying the mass ratio of AA to DMAEMA, biocompatible PAA-co-PDMAEMA eutectogels with high transparency (90 %), widely tunable mechanical properties (0.059–2.00 MPa), favorable conductivity (∼10−2 S m−1), remarkable anti-freezing property (−93 °C) and low-temperature adhesion (1.13 MPa in −30 °C) could be successfully prepared. The strong PAA2-co-PDMAEMA eutectogel displayed potential as shape-memory materials, while the flexible PAA4-co-PDMAEMA eutectogel exhibited great prospect as multifunctional wearable sensor. More importantly, the eutectogel-based flexible sensor possessed excellent strain durability (∼1000 cycles) and high temperature sensitivity (up to −15 % °C−1), suggesting intensive potentials in wearable electronic devices. In view of the diversity of monomers and DESs, the one-pot copolymerization strategy can be applied to other electrolyte monomers and eutectogel systems, offering a feasible and generic design method to regulate eutectogel microstructures and properties.