Optically active centers, chiral smectics

Requirements for the FLC moiety are as follows (i) the LC group includes a chiral center to exhibit an optical activity (ii) the LC group or molecule has a smectic phase with a non-zero tilt angle, that is, a chiral smectic C phase and (iii) the LC group has a non-zero dipole moment that is perpendicular to a molecular long axis. According to these requirements, three types of polythienylene derivatives containing the fluorinated asymmetric moiety in the LC side-chains were synthesized. The polymer structures are shown in Scheme 12.4. 

Incorporating a chiral center into a molecule confers chirality to it, and in solution it will display conventional optical activity. However, this does not necessarily mean that liquid crystal phases composed of chiral molecules will display optical activity. If the liquid crystal phase does exhibit optical activity, this is denoted with an asterisk, e.g., N or S. Of the smectic phases only those with molecules tilted within the layers exhibit optical activity. In some rare cases an orthogonal smectic phase can exhibit features not seen in the achiral version, e.g., the 5 phase exhibited by some chiral compounds exhibits a twist grain boundary phase. ... 

The formation of a chiral center on addition of a substituent to a flexible fr agment and the cholestmc polymo and chiral polymeric smectics that result are of qiecial interest Optically active (+)3-methyladipic acid in association with 1,4-dioxy-a-methylstilbaie [33], an q)tically active (+) isomer of 3-methyl-1,6-hexanediol [34], was used as the monomer for these purposes. The most... 

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