Columnar phase structures of an organic-inorganic hybrid functionalized with eight calamitic mesogens

A liquid-crystalline octapode, formed by laterally connecting calamitic mesogens to an inorganic silsesquioxane cube through flexible siloxane spacers, is studied using polarized light microscopy, differential scanning calorimetry (DSC) and X-ray diffraction (XRD). The studies are extended to mixtures of the octapode with the respective monomer mesogens. The monomer and the octapode show a nematic phase. At lower temperatures, the octapode exhibits additionally a columnar hexagonal phase (p6mm lattice), which, on further cooling, undergoes a transition to a columnar rectangular phase (p2gg lattice). A similar phase-transition sequence is observed for mixtures of the octapode with moderate concentrations of the monomer. The columnar - columnar transition is discussed combining XRD and DSC results, and a possible model of the molecular self-organization is presented.