Low-Temperature Structural Study of Smectic C_A* Glass by X-ray Diffraction

The liquid crystalline compound, forming the glass of the smectic C_A* phase, is investigated by X-ray diffraction in the 18-298 K range. The characteristic distances within the smectic C_A* phase are determined, and the specific volume is estimated. The electron density profile along the smectic layer normal is inferred and compared with the results of the density functional theory calculations. Observations of the selective reflection of the visible light investigate the helical ordering within the smectic C_A* glass. The results indicate slow change with temperature of the smectic layer spacing, intermolecular distances, and electron density distribution below the glass transition temperature. The change in the temperature dependence of the specific volume is well below the glass transition temperature. Meanwhile, the relative range of the short-range order within the smectic layers and the helix pitch are rather constant in the glassy state.