Volumetric pretransition in cholesterics

Abstract

Volumetric studies of the phase transitions in the following cholesterol derivatives are reported: cholesteryl chloride, C. laurate, C. myristate, C. nonanoate, and C. oleate. Pretransition volumetric behavior in the smectic, cholesteric, and isotropic phases is interpreted in terms of a ’’critical’’ exponent. In the isotropic phase the data are consistent with the de Gennes–Landau theory. The transformation from the cholesteric focal conic texture to the ’’blue phase’’ has a transition enthalpy and volume of approximately 5% of the transition to the isotropic phase.