Columnar Mesophase Formation of Cyclohexa‐m‐phenylene‐Based Macrocycles |
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Authors: | Wojciech Pisula Dr Marcel Kastler Dr Changduk Yang Dr Volker Enkelmann Dr Klaus Müllen Prof?Dr |
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Institution: | 1. Present address: Degussa AG, Process Technology & Engineering, Process Technology—New Processes, Rodenbacher Chaussee 4, D‐63457 Hanau‐Wolfgang, Germany;2. Max‐Planck‐Institut für Polymerforschung, Ackermannweg 10, D‐55128 Mainz, Germany, Fax: (+49)?6131‐379‐350 |
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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 π‐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 π‐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. |
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Keywords: | cross‐coupling macrocycles mesophases phase transitions self‐assembly |
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