Supermolecular Liquid Crystals - Liquid Crystalline Functional Assemblies and Their Supramolecular Structures - page 28

core has been reported, which provide six or eight primary (radial) branches
for derivatization, allowing an increased packing of the mesogens around the
dendritic core at earlier generations; moreover, the rigid framework of the
silsesquioxane cores offer the possibility of a contrasting comparison with
dendrimers derived from entirely flexible scaffolds. The structures of the
hexa- and octa-silsesquioxanes are shown together in Fig. 31.
A 1 example, 35 , of a nematogenic supermolecule possessing an oc-
tasilsesquioxane central core is shown in Fig. 32 [83]. The material, by virtue
of possessing laterally appended mesogenic units, is nematic, where the ne-
matic phase is enantiotropic by two to three degrees. On heating from the
solid state it exhibits a crystal to nematic phase transition, but on cooling
back to the solid it forms a glass, which is usually the case for supermolecules
with laterally appended mesogens.
Fig. 31 The structures of the hexa- and octa-silsesquioxanes cores for use as scaffolds