Mesogen, chiral

Figure 6. Schematic representation of LC elastomers prepared from chiral combined main-chain/side-chain copolymers, d] main-chain mesogens Idl side-chain mesogens chiral groups [7],...

Due to the important role of chirality in liquid crystals, a large number and variety of chiral chemical compounds have been developed. This chapter describes the most important molecular fragments and classes of chemical structures (Section 4.2) which provide both chirality and mesogenic properties. The form of chiral phases depends on the principles of the mesophase formation (Section 4.3). Some relations between the molecular chirality and the appearance of mesophase chirality are discussed and chiral dopants are classified (Section 4.4). With respect to the mesophase behavior and to optical and electro-optical applications, it is important to know how the mesogenic chirality can be modified, e.g., chemically by photoisomerization, or by changes of temperature or composition for certain suitable compounds (Section 4.5). Finally, chiral liquid crystals provide not only optical and electro-optical applications but also applications in Chemistry, e.g., as chiral solvents for synthesis, chiral stationary phases in chromatography, or chemical sensors (Section 4.6). 

Figure 20 (A) A polysiloxane copolymer having benzoic acid sidechains complexed with a mesogenic chiral stilbazole derivative [105], (B) A dipyridil complexed with two monofunctional acids showing Tsn = 166.5°, Tni = 178.5°C. Compare with the open assembly in Fig. 2A (Ref. 7a).

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