Polarity-sensitive switching nematic system from the assembly of achiral tripod-shaped and rod-shaped molecules

Here we report a nematic system showing polarity-sensitive switching behavior. An achiral rod-shaped liquid crystal (LC) and an achiral tripod-shaped dopant assembled each other and formed a unit block with strong electric dipole moment. This unit block has a shape of a tripod with extended legs and showed a macroscopic polarization under the electric field. Although the pure LC never showed polarity-sensitive switching, but the optic axis of the assembled unit blocks rotated clockwise or counterclockwise depending on the sign of the applied field. The threshold field to show the polarity-sensitive switching was lower in the sterically assembled sample (0.1 V/μm) than in the hydrogen-bonded one (1.3 V/μm) and the field response time was much faster in the former case. The inverse of the response time of the sterically assembled sample was linearly proportional to the strength of the electric field in the strong field regime and this also indicates the polar property of the doped nematic system.