Elasticity of Blue Phase I of Cholesteric Liquid Crystals

Normal shear modes of axial symmetry were excited in polycrystalline samples of blue phase I. An average shear modulus, $E$, is determined from the frequencies of these modes. $E$ is found to vary by nearly two orders of magnitude throughout the blue-phase temperature range. The authors report the first observation of faceted single crystals of blue phase I growing from the isotropic phase. These have enabled them to determine the blue phase I lattice constant.