Optical Rotatory Dispersion in Single Crystals of the Cholesteric Blue Phases

Abstract

Large quadratic single crystals (0.5 mm on a side) of Blue Phase I and Blue Phase II were rown using both pure cholesteryl esters and mixtures of cholesteryl esters. The optical rotatory dispersion of these single crystals was studied in the wavelength region 220–600 nm. All spectra show a single first order anomalous region, indicating that the orientation of the single crystals is nearly perfect in both Blue Phases. Sometimes the second order anomalous region can also be observed at very short wavelengths. A slight asymmetry in the first order peaks provides a quantitative estimation of the small lack of perfect orientation present. All single crystals were grown from the “Fog Phase”, which also possesses a characteristic optical rotatory dispersion spectrum.