Mesomorphic solid

All solid forms lacking order to a substantial degree and ordered liquids (smectic, nematic) are called at times mesomorphic forms. 

In this subsection some examples are presented of polymorphic polymers, for which one or more forms are solid mesomorphic, in the sense described in the Sect. 2.1. Let us recall that in this review we will not deal with liquid mesomorphic forms. 

It is, possibly, also worthy to cite the relevance of some mesomorphic forms in the optimization of the drawing conditions to get highly oriented manufacts although this is, possibly, mainly related to the peculiar morphological organization of these solid mesomorphic forms. 

A compound which displays liquid crystal properties is referred to as a mesogen and said to exhibit mesomorphism. Liquid crystals may be considered either as disordered solids or ordered liquids, and their properties are very dependent on temperature and the presence or absence of solvent. In thermotropic liquid crystals the phases of the liquid crystals may be observed to change as the temperature is increased. In lyotropic liquid crystals the ordered crystalline state is disrupted by the addition of a solvent, which is very commonly water. For these systems temperature changes may also be... 

As indicated above in chiral mesophases, the introduction of a functional group in mesogenic stmctures offers the opportunity to achieve functional LCs. With this aim, mesomorphic crown-ether-isocyanide-gold(I) complexes (26) have been prepared recently [38]. The derivatives with one alkoxy chain show monotropic SmC mesophases at or close to room temperature. In contrast, the complexes with three alkoxy chains behave as monotropic (n = 4) or enantiotropic (n > 4) LCs. The structure of the mesophases could not be fully eluddated because X-ray diffraction studies in the mesophase were unsuccessful and mesophase characterization was made only on the basis of polarized optical microscopy. These complexes are luminescent not only in the solid state and in solution, but also in the mesophase and in the isotropic liquid state at moderate temperatures. The emission spectra of 26a with n=12 were... 

Further work will be related to the development of curable systems as well as to a broader examination of the phase morphologies in the solid state. In addition, the dependence ofthe technologically relevant selectivity in gas permeation on the type and size of the resulting mesomorphous phases is currently under investigation. 

Mesitylene, production from acetone, 1 164 Mesityl oxide, 14 589-590 characteristics of, 16 337 hydrogenation, 16 337-338 hydrogen peroxide treatment of, 16 338 Z-menthol from, 24 520 production of, 16 336-337 production from acetone, 1 164, 174 Mesogenic diols, 25 460 Mesogenic molecules, solids of, 15 82 Mesogens, 24 53, 54 Mesomixing, 16 683 Mesomorphic behavior, 24 53-54 Mesomorphic phase transitions, 15 102 Mesomorphism, 15 81. See also Liquid crystalline materials Mesophase pitch-based carbon fiber, 26 734-735... 

Some drug substances can form mesophases with or without a solvent [19-26]. In the absence of a solvent, an increase in temperature causes the transition from the solid state to the liquid crystalline state, called thermotropic mesomorphism. Lyotropic mesomorphism occurs in the presence of a solvent, usually water. A further change in temperature may cause additional transitions. Thermotropic and/or lyotropic liquid crystalline mesophases of drug substances may interact with meso-morphous vehicles as well as with liquid crystalline structures in the human organism. Table 1 presents drug substances for which thermotropic or lyotropic mesomorphism has been proved. 

The term sorption is used to describe every type of capture of a substance from the external surface of solids, liquids, or mesomorphs as well as from the internal surface of porous solids or liquids (Skoulikides, 1989). Depending on the type of bonding involved, sorption can be classified as follows. 

The corresponding pyrazole mononuclear derivatives [AuCl(pzH)] have been prepared with the same ligands (Figure 7.41) [38]. Only the monosubstituted non-mesomorphic pyrazole leads to a liquid crystal, not the disubstituted mesomorphic ligand. The complex displays a SmA mesophase on cooling to 69.2 °C, although this is mixed with some crystallization. Moreover, this derivative is luminescent at 77 in the solid state. In addition, the corresponding trinuclear and mononuclear derivatives, namely [ Au(pz) 3] and [Au(Hpz)2]+, which could be expected to be liquid crystals are non-mesomorphic. 

An even more dramatic example of the potential lack of selectivity afforded to the Norrish II reactions of ketones by supposedly very ordered systems than that described in the 76 systems is provided by neat samples of the mesomorphic alkanophenones (81) [278]. These molecules are capable of existing in nematic and smectic B mesophases (see Figure 16) as shown in Scheme 42. The instability of the monotropic smectic B phase of 81a and smectic B phase of 81b did not allow their photoreactions to be examined these smectic phases became solids soon after the initiation of irradiation. 

As pointed out in Chapter 1, supramolecular chemistry comprises two broad, partially overlapping areas covering on the one hand the oligomolecular supermolecules and, on the other, the supramolecular assemblies, extended polymolecular arrays presenting a more or less well-defined microscopic organisation and macroscopic features depending on their nature (layers, films, membranes, vesicles, micelles, microemulsions, gels, mesomorphic phases, solid state species, etc.). 

Solid-state NMR experiments showed the dynamic nature of the disordering. It has been possible to monitor the type and the changes of segmental motions within the mesomorphic phase and at the corresponding phase transitions for typical examples. The thermal... 

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