Molecular Structure and Liquid Crystalline Properties: The Effect of the Terminal Hydroxy Group on Mesomorphic Properties

The thermal properties of 4-hydroxyphenyl 4-(4-alkoxybenzoyloxy)benzoates (1), 4-(4-alkoxyphenox-ycarbonyl)phenyl 4-hydroxybenzoates (2), 4-(4-alkoxybenzoyloxy)phenyl 4-hydroxybenzoates (3), 4-hydroxyphenyl 4-(4-alkoxyphenoxycarbonyl)benzoates (4) and some related compounds have been examined. The nematic-isotropic and smectic A-nematic transition temperatures are compared with those of the related compounds having a methoxy group and a chlorine atom instead of the hydroxy group. The results indicate that the mesomorphic properties are almost independent of the hydrogen bonding at the terminal position. On the other hand, the effect of the hydrogen bonding is recognized in the smectic properties in some binary mixtures consisting of the hydroxy compounds and aryl acids. The effect of hydrogen bonding on mesomorphic properties is discussed.