Thermotropic classical

G. Vertogen and W. H. De Jeu. Thermotropic Liquid Crystals, Fundamentals Springer Series in Classical Physics, Springer-Verlag, Berlin (1988), Vol. 45. 

This study has concentrated on the defects observed in lyotropic lamellar phases, and it has put into evidence the specific character of the textures compared to classical thermotropic smectic phases. In leci-... 

One of the most classic examples of chiral expression in thermotropic liquid crystals is that of the stereospecific formation of helical fibres by di-astereomers of tartaric acid derivatised either with uracil or 2,6-diacylamino pyridine (Fig. 9) [88]. Upon mixing the complementary components, which are not liquid crystals in their pure state, mesophases form which exist over very broad temperature ranges, whose magnitude depend on whether the tartaric acid core is either d, l or meso [89]. Electron microscopy studies of samples deposited from chloroform solutions showed that aggregates formed by combination of the meso compounds gave no discernable texture, while those formed by combinations of the d or l components produced fibres of a determined handedness [90]. The observation of these fibres and their dimensions makes it possible that the structural hypothesis drawn schematically in Fig. 9 is valid. This example shows elegantly the transfer of chirality from the molecular to the supramolecular level in the nanometer to micrometer regime. 

The subject of liquid crystals has now grown to become an exciting interdisciplinary field of research with important practical applications. This book presents a systematic and self-contained treatment of the physics of the different types of thermotropic liquid crystals - the three classical types, nematic, cholesteric and smectic, composed of rod-shaped molecules, and the newly discovered discotic type composed of disc-shaped molecules. The coverage includes a description of the structures of these four main types and their polymorphic modifications, their thermodynamical, optical and mechanical properties and their behaviour under external fields. The basic principles underlying the major applications of liquid crystals in display technology (for example, the twisted and supertwisted nematic devices, the surface stabilized ferroelectric device, etc.) and in thermography are also discussed. 

According to Fig. 3, classical thermotropic smectic phases of amphotropic liquid crystals are (SmA ), colunmar hexagonal (Col ), bicontinuous cubic (Cub, i), or discontinuous cubic (Cubjis) [169]. All these meso-phases include a disclination surface between the hydrophilic and the lipophilic parts of the unordered molecules. This surface can be uncurved (SmA), curved in one direction (columnar), curved in two directions with the same sign (discontinuous cubic), or curved in two directions with opposite sign (bicontinuous cubic). 

In the classical view only membranes and their components seem tolerable, with their close bilayer similarities to thermotropic smectics and head/tail abstracted lyotropics [7a, 33p, q, 54-57]. While nucleic acids and proteins represent both structure and system individualities, membranes, as huge collectives of highly differentiated mem-... 

Figure 26. (Bio)mesogenic order-disorder patterns rather than geometric anisotropies as general preconditions for the appearance of mesophases a) classical thermotropic cyanobiphenyl nematic [25 a, 51e] and thermotropically designed steroid hormone cholesteric [17 a, c, d, 26 f, 51 a, s, u] b) protein-j3-sheet simulative diacylhydrazine smectic [17 a, c, d, 26f, 511] c) hexaalkanoyloxybenzene discoid [28 a, 51c] ending the century of rod-like dominance d) lyotropic poly(L-glutamic acid) [51 d, 52 k, 1] changing with an alkyl-disorder shell from lyotropic to thermotropic [58e] e) ds A-RNA lyotropic [52n-w, 75] f) am-photropic(L-Lys) /RNA recognition complex [17,18, 75],...

Flussige Kristalle in Tabellen Figure 14. Common central parts of classical thermotropics... 

Figure 17, Cycloaliphatic and steroidal central parts in classical thermotropics (3S)...

In this way the old Vorlander effect of directing mesophase systems by interaction possibilities of small amounts of inducers, elucidated and used in theoretical and practical aspects by Stegemeyer and his group mainly in the field of classical thermotropics,... 

Chiral mesophases can be obtained from sugars by several strategies. Many cellulose derivatives show thermotropic and lyotropic cholesteric phases [16]. Peracylated sugars can be used as chiral dopants for discoid nematic phases [17]. Also classical cholesteric and ferroelectric phases can be obtained from carbohydrate-based compounds [18]. In this case, chiral oxa-heterocycles are prepared from sugars. Figure 4.8 shows a chiral twin compound prepared from mannitol [19]. 

---