Synthesis and characterization of liquid crystalline silsesquioxanes

With the goal of developing diverse building blocks for nanocomposite materials, we have now learned to synthesize liquid crystalline materials by appending mesogenic groups to cubic silsesquioxane cores (LC cubes) via hydrosilylation of allyloxy functionalized mesogens (4, 5, 8, and 9) with octakis(dimethylsiloxy)octasilsesquioxane (Q(8)M(8)(H)). On average, hydrosilylation leads to cubes with an average of five LC groups attached, which differ from the more "regular", fully LC-substituted analogues reported previously. Despite the structural irregularity, three out of the four penta-LC-cube derivatives (II-IV) show LC transitions, with a tendency to form SmA. LC behavior was characterized using differential scanning calorimetry, polarized light microscopy, and X-ray diffractometry.