Highly Robust and Low Frictional Double‐Network Ion Gel

Reducing friction is important to improve the lifetime and energy efficiency of mechanical systems. Since human joints with gel‐like structure possess a coefficient of friction as low as 10–3, gel materials are recognized as a useful example for designing low frictional materials. Ion gels incorporating ionic liquids (ILs) as swelling agent is expected to be stable gel lubricant since high thermal stability and negligible volatility of ILs can maintain swelled state of gels even under harsh conditions. In this study, we newly synthesized a double network (DN) ion gel composed of an ionic liquid, N,N‐diethyl‐N‐(2‐methoxyethyl)‐N‐methylammonium bis (trifluoromethylsulfonyl)imide (DEME‐TFSI) and an ionic liquid polymer composed of the derivative of DEME‐TFSI, poly (N,N‐diethyl‐N‐(2‐methacryloylethyl)‐N‐methylammonium bis (trifluoromethylsulfonyl)imide) as a first network and neutral poly(methyl methacrylate) as a second network. The obtained DN ion gel showed high compression strength and it was thermally stable until 300 °C. The stable COF after repeated measurements at high temperature or vacuum conditions showed the durability of DN ion gels even under harsh conditions. The results obtained in this study shed light on the fabrication of lubricant gels with high mechanical strength and robustness, which are expected to be new candidates for enegy conservation. Double‐network hydrogels with high toughness and low friction are expected as lubricant gel materials, while water evaporation has prevented its industrial usage. The combination of an ionic liquid and its compatible polymers results in a robust low frictional ion gel with high compression strength (30 MPa) and stability under high temperature (80 °C) or vacuum (2.2 × 10−4 Pa).