Generating tunable structures in glassy materials: Smectic-like layering in glasses of a liquid crystal system prepared by vapor deposition

Anisotropic packing, particularly in highly ordered liquid crystalline configurations, has been shown to be useful in organic electronic and optoelectronic applications. In this work, vapor deposited glasses of a model smectic liquid crystal-forming molecule, itraconazole, are investigated. The films are characterized using x-ray scattering, FTIR and spectroscopic ellipsometry, and are found to exhibit unprecedented structural and optical anisotropy for a macroscopically homogeneous solid. A smectic-like layered structure is observed in the glasses that are prepared by depositing the glass at a substrate temperature during deposition (T$_{sub}$) maintained below the glass transition temperature, T$_{g}$, of the molecule. The layer spacing, and the associated average tilt angle of the molecules, is found to be tunable as a function of T$_{sub}$. The layer spacing reduces by 16\% as T$_{sub}$ is lowered. These features are retained in the films when heated to at least T$_{g}$ of the molecule.