Molecular Structure and Flexibility

Although liquid crystalline phases can be formed from entirely rigid units such as rods and ellipsoids, all liquid crystal molecules are partially flexible objects which can change their shape in a variety of ways. The extension of rigid-rod theories to account for flexibility is complex and has been the object of considerable effort for several years. It is now clear that simply relaxing the assumption of molecular rigidity is expected to have profound effects on phase behaviour. 

Analytical approaches to understanding the effect of molecular flexibility on orientational order have concentrated on both the isotropic-nematic and the nematic-smectic transition [61, 62] and mean field theory has shown that cholesteric pitch appears not to depend on the flexibility of the molecule [63]. 

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