Evidence for An Hexagonal Phase in Twisted Nematics

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Abstract
Sequences of microscopic photographies show different behaviors during the isotropic-cholesteric transition in a binary diagram untwisted nematic-cholesterol ester. For certain conditions, a mosaǐc texture arises between the isotropic liquid and the focal-conic texture, the germination of which gives evidence for an hexagonal symmetry. The large variation of pitch from the nematic phase to the pure cholesterol ester can explain these facts if we consider the Brazovskii's theory of cholesteric transitions.