First azulene liquid crystal with de Vries behavior and a SmA re-entrant phase

Abstract

De Vries-like materials show small layer shrinkages at the SmA to SmC transition and can therefore be applied in surface-stabilized ferroelectric liquid crystal displays. Here we report the synthesis and characterization of a new class of de Vries mesogens with a simple 2-phenylazulene-1-carbonitrile-based core. These materials exhibit an exceptionally small lower threshold for the maximum layer shrinkage of only 0.16%. One of the investigated compounds shows an orthogonal SmA re-entrance phase below the tilted SmC phase. This behavior has not been observed for achiral calamitic molecules before. The rationalization of the anomalous phase behavior might lead to a new design principle for liquid crystalline compounds showing re-entrant phases and de Vries behavior.