Phase morphology of a disk-sphere dyad molecule.

A disk-sphere dyad molecule was synthesized by attaching a discotic triphenylene molecule to a spherical polyhedral oligomeric silsesquioxane (POSS) molecule via esterification reaction. The self-assembly behavior of the dyad molecule was studied by differential scanning calorimetry, polarized light microscopy, X-ray diffraction (XRD), and transmission electron microscope. Two-dimensional (2D) XRD results showed the dyad molecules self-assembled into a lamellar structure, which composed of a crystalline POSS layer and a discotic-nematic triphenylene double-layer. The POSS layer consisted four layers of ABCA-stacked spherical molecules. The liquid crystalline triphenylene molecules were parallel and staggered in the double-layer. Computer simulation of the XRD intensity confirmed the proposed structural model. Compared with that of the POSS crystal in bulk (melting point at ca 220 $^{o}$C), the melting temperature of POSS crystal was dramatically decreased to 67 $^{o}$C, possibly due to effects of the asymmetry molecular shape and plasticization of the discotic triphenylene moieties between POSS layers.