Mesogens discotic

Most polymeric Hquid crystals are based on stiff rod-like molecular units which are called calamitic mesogens. There are some unusual polymers (which are not discussed here) that contain flat disk-like molecular units called discotic mesogens in which the disks form columnar arrays like stacks of poker chips. 

Discotic liquid-crystal phase, 13 371 Discotic liquid crystals, 15 96 Discotic mesogens, 20 79 Discounted cash flow return rate (DCFRR), 9 544-545... 

Mesogen eomposed of moleeules incorporating one or more metal atoms. Note yistdiWomesogens may be either calamitic or discotic mesogens. 

Figure 7.38 Schematic representation of the trinuclear discotic mesogens.

Figure 7.39 (a) Schematic representation of discotic mesogens with only three alkoxy chains (n = 7, 8) (b) schematic representation of the star-shaped dimer. 

Dirhodium tetraphosphine, for hydroformylations, 7, 252 Discodermolide, via ring-closing diene metathesis, 11, 218 Discotic mesogens mesophases, properties, 12, 202 properties, 12, 202 Diselenides... 

To some extent, the design criteria for discotic mesogens are somewhat simpler than those for their calamitic counterparts. In many cases, it is possible to choose a favorite disk-like molecule, then add 6-8 peripheral alkyl chains to generate a mesomorphic (i.e., hquid-crystalline) material. Thus, phthalocyanines, triphenylenes, truxenes, and many other systems will generate mesogenic (i.e., liquid-crystal-like) materials with appropriate substitution these examples are shown in Fig. 24. Note that it is not necessary for the mesogen to have a planar core. 

Liquid crystallinity can be attained in polymers of various polymer architectures, allowing the chemist to combine properties of macromolecules with the anisotropic properties of LC-phases. Mesogenic imits can be introduced into a polymer chain in different ways, as outhned in Fig. 1. For thermotropic LC systems, the LC-active units can be connected directly to each other in a condensation-type polymer to form the main chain ( main chain liquid crystalline polymers , MCLCPs) or they can be attached to the main chain as side chains ( side chain liquid crystalline polymers , SCLCPs). Calamitic (rod-Uke) as well as discotic mesogens have successfully been incorporated into polymers. Lyotropic LC-systems can also be formed by macromolecides. Amphiphihc block copolymers show this behavior when they have well-defined block structures with narrow molecular weight distributions. 

Fig. 18 Chemical structures of monomers with discotic mesogens...

This formation of nematic, lamellar and columnar phases within a single class of molecule leads to the idea that they can be considered as a missing link between calamitic and discotic mesogens. 

The system represents a discotic mesogen of an immense diameter (1.6 nm), with six flexible side chains. The crystalline phase is transformed at 115 °C to a broad nematic phase Nj) in which two discs have a parallel arrangement with an average distance of... 

A surprisingly efficient intermolecular photochemical [2 + 2] dimerization was achieved in the synthesis of belt-shaped cyclophanes by irradiation of arenoannelated [18]annulenes like 176 [116]. The highly selective threefold [27t+27t] cycloaddition yields dimers 177 in up to 68%. The efficiency of this dimerization process even at high dilution can be explained with the perfect preorganization of the discotic mesogenes 176. 

---