Sanidic mesophase

Note 5 Distinct biaxial mesophases are created when the molecular centers of mass are correlated within the layers. Such mesophases have been proposed for board-like polymers and have been called sanidic mesophases. 

Note 5 A biaxial nematic has the same structure as a disordered sanidic mesophase (see Definition 3.4, Note 2) it is recommended that the latter name be discontinued and the name biaxial nematic be used. 

Note 2 Short board-like shaped molecules usually form biaxial nematic mesophases. It is recommended that the use of the term disordered sanidic mesophases for such mesophases be discontinued (see Definition 3.3.1, Note 5). 

Sanidic mesophase in which the molecular stacks are packed regularly side-by-side with long-range order along a stack normal as well as along the long stack-axis. 

Note 2 A polymer LC consisting of macromolecules of board-lrke shape can be called a board-shaped polymer LC. Such polymers can form sanidic mesophases. 

It should be noted that 2D-mesophases formed by long side chains in a series of comb-like polymers (7) can not be attributed to columnar mesophases due to the lack of properties inherent to columnar mesophases. By the same reason sanidic mesophases (72) including 2D-ordered one are not to be classified as columnar ones. 

The sanidic mesophase results from a hindered rotation of the mesogenic units. It requires three distinctly different dimensions of the mesogens.This phase is generally observed in polymers with lateral side chains and very rarely in LMWLCs. In the case of polymers also the extension of the molecule in the direaion of the polymer chain contributes to a... 

Note 6 Sanidic structures are analogous to the columnar mesophases formed by disc-like molecules. 

Recent developments in the substitution of completely aromatic LC polyesters have produced polymers which show improved solubilities and reduced transition temperatures (29). The presence of these side groups provides a method for producing polymers that are compatible with other similarly modified polymers. In this way, blends of rigid and flexible polymers can be prepared. Substituents have included alkyl, alkoxy (30) and phenyl alkyl groups (21), some of which lead to mesophases that have been reported as being "sanidic" or board-like. This approach has been used with both polyesters and polyamides and has lead to lyotropic and thermotropic polymers depending on the particular composition used. Some compositions even show die ability to form both lyotropic and thermotropic mesophases (22). 

Fig. 1.1.10. Mesophases of discotic polymers (a) the hexagonal columnar phase. The diagram illustrates intercolumnar binding as well as intracolumnar back-folding of the main chain (Herrmann-Schonherr, Wendorff and Ringsdorf ) (b) the sanidic nematic phase composed of boards stacked parallel to one another (Herrmann-Schonherr et a/. ) (c) the columnar nematic phase (Ringsdorf...

Tetrasubstituted polyesters with long alkyl side chains on the hydroquinone moiety connected via ether or ester linkages have been reported [20 c] (Fig. 12). In these polyesters, the tetrasubstituted moiety can be considered as a discotic mesogen. The polyesters with Z = H are highly soluble and have low melting temperatures (T n < 100 °C) and low clearing temperatures in the range of 123-260°C. The type of mesophase formed is referred to as sanid-... 

FriedeP was the first who distinguished three main classes of liquid crystals, according to the different kind of orders in the mesophases nematic, smectic, and cholesteric. From the point of view of the geometrical shape of molecules, we divide the thermotropic LCs into calamitic phases (when the molecules are rodlike), sanidic phases (when the molecules are bricklike), and the discotic phases (when the molecules are disklike)... 

Figure 33. Mesophases of discotic polymers (a) hexagonal columnar phase (b) the board-like, or sanidic, nematic phase (c) the columnar nematic phase.

Mery, S., Haristoy, D., Nicoud, J.-E, Guillon, D., Diele, S., Monobe, H., Shimizu, Y. Bipolar carrier transport in a lameUo-columnar mesophase of a sanidic liquid crystal. J. Mater. Chem. 12, 37 1 (2002)... 

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