Mesomorphic system

Tihe term lyotropic mesomorphism is used to describe the formation of thermodynamically stable liquid crystalline systems through the penetration of a solvent between the molecules of a crystal lattice. In contrast to the thermotropic mesomorphism shown by many pure substances, lyotropic mesomorphism always requires the participation of a solvent. Lyotropically mesomorphous systems, however, are usually as sensitive to changes in temperature as thermotropic systems. So far, lyotropic mesomorphism has been observed almost exclusively in lipid systems containing water. Lipids that show lyotropic mesomorphism frequently... 

A similar approach with 4-nitrophenol also generated mesomorphic systems. This time, the mesophases were slightly more stable and some phases appeared to be enantiotropic (i.e., they became more stable than their crystal phase) (69). However, the beauty of the hydrogen-bonding approach to liquid crystals is that it is not always necessary to synthesize complete moleciiles. Thus, it was realized that if the 4-substituted phenols lowered the anisotropy as indicated in Fig. 53, the anisotropy ought to recover to give much more stable systems if the 3-substituted systems were used (Fig. 54) (69). That this approach was viable was... 

Other dendritic frameworks were used, but did not always yield to mesomorphic systems. For instance, the polyalkylarylether dendrimers functionalized by azobenzene mesogens failed to show any hquid crystalline property despite the mesomorphic side-group promoter [249]. 

On the other hand, the molecular trapping capacity of the networks (150 pmol/g of polymer) was shown to be much greater than that of most of the previously studied non-mesomorphous systems [197]. 

Multicomponent Systems. There are many mesomorphic systems in which at least two components are present. The most common variety is called a lyotropic mesophase it consists of a molecule with a hydrophilic and a hydrophobic portion dissolved in water. Since at least two components are present, there can be a coexistence of more than one phase. The classical method of investigating such systems consisted of mixing the two components together, centrifuging until the two phases were separate, and analyzing each phase. By NMR it is possible to make a qualitative analysis of each phase without separation in many cases. The sodium palmitate (NaP)-deuterium oxide (D20) system shows the sort of information which can come from such an analysis. The NaP-D20 system exists in several different mesomorphic phases in addition to the isotropic liquid and crystalline phases (6, 23, 36, 37). The mesophases are mainly of the smectic type although the lyotropic mesophase normally called middle does not have all the characteristics of a true smectic phase. 

The NMR line widths can be used to determine phase transitions in both one- and multicomponent mesomorphic systems. Transition temperatures and phase boundaries determined by NMR are usually in good agreement with those determined by other methods. The NMR data can therefore be used to construct reliable phase diagrams. They are most useful in systems where separation of the mesophase from other phases is difficult or impossible. 

General Aspects on Static Quadrupole Effects of Mesomorphous Systems... 

The structure of PMCS-6 mesophase cannot be described in terms of the conventional classification used for organic mesophase polymers. From our viewpoint, PMCS-6 are the novel class of mesomorphic systems. 

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