A Study of Liquid Crystalline Properties and Their Relation to the Molecular Structure of Novel Ethylene Derivatives

摘要

A novel homologous series α-4-[4'-n-Alkoxy benzoyloxy] benzoyl β-4"-methoxy phenyl ethylenes of 12 homologue substances is presented and comprises of 5 compounds (heptyl to tetradecyl) that exhibit both a smectic and a nematic phases. The pentyl, hexyl, and hexadecyl homologues only exhibit the nematic without exhibition of any smectogenic property. The methyl to butyl homologues are not liquid crystalline. All novel liquid crystal (LC) substances of novel series are enantiotropically mesomorphic. The textures of nematogenic homologues are threaded or Schlieren and that of the smectogenic homologues are typical of the smectic A or C. Analytical and spectral data support the molecular structures. Solid-mesomorphic or isotropic, Sm-N, and N-isotropic transition curves of a phase diagram behave in a normal manner. An odd-even effect is exhibited by the Sm-N and N-isotropic transition curves. Thermal stabilities for the smectic and nematic mesophases are 118.0℃ and 157.0℃, respectively. The Sm-N mesophase length is between 13℃ and 21℃, whereas the N-I mesophase length varies between 20° C and 46° C. The liquid crystal properties of the novel series are compared with known structurally similar homologous series.