Novel 6,6′-Difluoro-substituted Binaphthyl Derivatives as Chiral Dopants for Fluorinated Nematic Liquid Crystals

We synthesized novel alkyl-bridged or nonbridged 6,6′-difluorinated binaphthyl derivatives and their analogues, and investigated their helical twisting properties in a fluorinated nematic liquid crystal. Since the bridged structure is rigid with a fixed dihedral angle between the two naphthalene moieties, the bridged binaphthyl derivatives showed large absolute values of the helical twisting power (HTP) with low temperature dependence. The alkyl chain length of the bridged part affected the HTP of the fluorinated binaphthyl derivatives because the dihedral angle changes depending on the number of alkyl carbons. Additionally, the solubility of the fluorinated derivative in the fluorinated nematic liquid crystal was high due to good compatibility between fluorinated compounds.