Twist grain boundary phases compounds

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. ... 

Table 10.2. Some chemical compounds showing twist grain boundary (TGB) phases.

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