Triptycene-containing bis(phenylethynyl)benzene nematic liquid crystals

Abstract

We report the synthesis of a new class of nematic liquid crystals with triptycenes built into a p-dialkoxy-bis(phenylethynyl)benzene mesomorphic core. Triptycenes are appended on the center or terminal ring of the mesogen, leading to symmetric liquid crystals and reduced symmetry liquid crystals, respectively. Both types displayed monotropic behavior, with the asymmetric compounds having unusual phase behavior, lacking distinct crystallization transitions, and forming a glassy mesophase. A chiral analogue was found to be non-mesomorphic, but induced chiral nematic phases when doped into achiral triptycene-containing analogues. Rotation is physically hindered normal to the director and, hence, this new liquid crystal architecture may allow for the synthesis of a single component liquid crystal that displays a biaxial nematic phase.