THE INFLUENCE OF THE LIQUID-CRYSTALLINE CORE GEOMETRY ON THE MESOGENICITY OF NOVEL CHIRAL 2-(4-SUBSTITUTED-PHENOXY)PROANONITRILES

The synthesis and characterization of seven novel (R)-2-(4-substituted -phenoxy)propanonitriles are described. The propanonitriles were prepa red to evaluate their potential use as thermochromics and ferroelectri c dopants, as well as to determine their twist sense properties. The m aterials exhibit smectic and chiral nematic phases of high thermal sta bility; the mesogenic behaviour of the nitriles is directly related to the type of two-ring core unit employed. The effects of the different molecular geometries and polarizabilities of the liquid crystalline c ores on mesophase stability are discussed, particularly in relation to other members of this series. The chiral nematic phase of the propano nitriles is assigned as having a left-handed twist sense from contact preparation studies, and this is in agreement with rules relating abso lute configuration and molecular structure to helical twist sense.