Low mid-infrared absorption tolane liquid crystals terminated by 2,2-difluorovinyloxyl: synthesis, characterization and properties

The synthesis and characterization of new 2,2-difluorovinyloxyl terminated tolane liquid crystals are reported. The mesomorphic properties, mid-wave infrared (MWIR) absorption and birefringence were investigated. The results show that these materials exhibit low absorption loss, a wide nematic phase range, a low melting point and high birefringence. The influences of fluorine substitution and terminal groups were discussed. Moreover, a room temperature eutectic mixture is formulated with relatively high birefringence (Δn = 0.254 at λ = 4 μm), modest dielectric anisotropy (Δε = 2.37), low viscosity (182.9 mPa s) and a low absorption coefficient in the 3–5 μm region.