Solvent-free poly(ionic liquid) elastomers with high stretchability and adhesion for flexible sensing applications

As a flexible conductive material, ionogels inherently suffer from limitations to the liquid components, potentially leading to leakage and evaporation. Here, a class of solvent-free poly(ionic liquid) elastomers (PILEs) is prepared through the copolymerization of imidazolium ionic liquid monomers with different functional groups (benzyl, butyl, heptyl, and decyl) and soft acrylate monomers. The transmittance of the PILEs in the visible range (400–800 nm) was 91 %, and the decomposition temperatures of PILEs were close to 320 °C. The PILEs with benzyl groups exhibited a tensile strength of 0.87 MPa and an elongation at break of 960 %, attributed to the structural rigidity of the benzene ring and cation-π interaction. The elongation at break of the PILEs with decyl groups reached 2920 %, attributed to the synergy of entanglement and hydrogen bond. The PILEs can adhere to various substrates and maintain adhesion across a wide temperature range (–10 °C to 60 °C). The PILEs with benzyl groups also yielded room-temperature ionic conductivity of 1.33 × 10 −4 S/m and exhibited good sensitivity to strain and temperature. These combined properties make the PILEs a candidate for flexible sensor.