title: Columnar mesophase formation of cyclohexa-m-phenylene-based macrocycles.
abstract: Two novel discotic macrocycles, substituted cyclohexa-m-phenylene (CHP) and cyclo-3,6-trisphenanthrylene (CTP), and the linear oligomer 3,3':6',3''-terphenanthrene (TP) as a model substance have been synthesized by repetitive cross-coupling reactions. To correlate the molecular design with the supramolecular architecture and the established macroscopic order, 2D wide-angle X-ray scattering experiments were performed on mechanically extruded filaments. At room temperature in their crystalline phases, all three compounds revealed columnar assemblies in which the macrocycles self-organized by pi-stacking interactions. The degree of macroscopic order was found to depend upon the planarity and stiffness of the aromatic core. The flexible CHP ring showed a poor macroscopic order of the columnar structures and a low isotropization temperature, whereas the more-planar, less-flexible CTP self-assembled into well-defined superstructures. The larger pi-stacking area and the more-pronounced intermolecular interactions for CTP led to the formation of a mesophase over a very large temperature range. The surprising columnar organization of the "open" TP system was explained by back-folding of the molecule into a ringlike structure.
authors: Max-Planck-Institut für Polymerforschung, Ackermannweg 10, D-55128 Mainz, Germany.
authors: Wojciech
authors: W
authors: Pisula
authors: Marcel
authors: M
authors: Kastler
authors: Changduk
authors: C
authors: Yang
authors: Volker
authors: V
authors: Enkelmann
authors: Klaus
authors: K
authors: Müllen