Formation of Optically Isotropic Cubic Phase Based on Chiral Recognition in Dichiral Compounds

Abstract

Dielectric and ¹³C-NMR measurements have been made to investigate the optically isotropic (IsoX) phase in dichiral compounds. The dielectric dispersions in the IsoX phase was found to be almost the same as that in the isotropic liquid (Iso) phase. The similar dynamic behavior in the Iso and IsoX phases is also observed in the ¹³C-NMR measurement. These experimental facts suggest that the IsoX phase is not only optically isotropic but also has no cooperative motion, as in the Iso phase. An endothermic enthalpy change from the SmC* to IsoX phases associated with marked supercooling suggests that the formation and growth of the IsoX phase cannot be made in the Iso phase. Based on the phase diagrams of the binary mixtures of the stereoisomers, molecular chiral recognition was suggested to exist to form the IsoX phase.

Key Words:

• chirality
• cubic phase
• dichiral compound
• dielectric dispersion
• ¹³C-NMR
• phase diagram
• endothermic enthalpy change
• DSC