Polymorphism of Liquid Crystals

4-methoxybenzylidene-4 -butylaniline was the first compound which showed the liquid crystal phase at room temperature. The chemical formulae of MBBA is as follows 

MBBA shows only the nematic liquid crystal phase (denoted as N phase), its phase sequence being 

A few liquid crystals have a more complicated phase behavior, showing more than one liquid crystal phase. The series of terephthalylidene-bis-alkylanilines (TBnA) is particularly interesting in presenting an unusually broad polymorphism. For example, TPBA 

Molecules with non-symmetric carbon atoms may exhibit a chiral structure, e.g., the compound (8SI) of chemical formulae 

We now introduce the classification of the liquid crystal phases and their structural features. 

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