Self-assembled molecules discotic liquid crystals

It was quickly recognized that chirality would play an important role in discotic liquid crystals, not only for the possibility of creating cholesteric and ferroelectric liquid crystals but also as a tool for studying the self-assembly of these molecules as a whole, both in solution and in the solid state. However, initial studies revealed that expression of chirality in discotic liquid crystals was not as straightforward as for liquid crystals derived from calamitic molecules. More recently, with the increase in interest in self-assembly and molecular recognition, considerably more attention has been directed to the study of chiral discotics and their assemblies in solution. The objective of this chapter is... 

Discotic liquid crystals are a prototypical self-assembled columnar system [9-13]. This class of liquid-crystalline compounds is relatively new, discovered in 1977 by Chandrasekar and coworkers [14,15]. The assembly motif, shown in Figure 2, for this class of compounds has an aromatic core that is surrounded by hydrocarbon chains. These disk-shaped molecules then stack to form columns. These one-dimensional stacks aggregate to form arrayed columns. When the columns have a circular cross-section they typically stack into a hexagonal arrangement as shown in Figure 2(a). Some of the original discotics were hexa-substituted phthalocyanines (1), benzenes (2), and triphenylenes (3), shown in Figme 2(b). The self-assembly of classical discotics will not be presented in depth here because it has been a focus of several comprehensive reviews [9-15]. 

Thermotropic Liquid Crystals. - Organic molecules, having aromatic rings or unsaturations thus producing elongated shapes, and also polymeric molecules often show thermotropic phase behavior. Mesomorphism comprises typically nematic, smectic A and B, and cholesteric thermotropic phases, but in several cases columnar, discotic and rod-disk self-assembly shapes of thermosensitive mesogens have been observed. 

In liquid-phase carbonizations, the mechanisms are completely different from those in the solid phase. It is via liquid-phase carbonizations (but not all liquid phases) that graphitizable forms of carbon result. How does this come about The explanation takes us to a quite different subject area, that of anisotropic aromatic, discotic, nematic liquid crystals (called mesophase) formed as a result of growth and self-assembly of the constituent polycyclic aromatic molecules of the parent material. These usually are the highly aromatic coal-tar pitches, a liquid product from the making of metallurgical coke, from aromatic pitches synthesized by the petroleum industry as well as polycyclic aromatic model compounds. 

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