Optical Properties of the Isotropic Mesophase Formed by Cholesteryl Esters

Abstract

Optical rotatory dispersion (ORD) and selective reflection spectra (SR) of the isotropic so‐called “blue‐phase” (BP) of cholesteryl myristate and nonanoate have been studied. The anomalous ORD effect as well as the SR band is sharply separated from the corresponding effect of the cholesteric phase and positioned at longer wavelength. The sign of the ORD curve and the reflection of left circularly polarized light indicate any left‐handed helical arrangement in the BP. The refractive index of the isotropicBPis found to be related to that of the birefringent cholesteric phase by the Vuks formula. Requirements of structural models for theBPare discussed in terms of the experimental results.