Properties of the Liquid Crystals Formed by Certain 4-(2′-Pyridyl)phenyl and 4-(4′-Pyridyl)phenyl 4″ -n-Alkoxybenzoates

Abstract

Nine members of each of two homologous series of esters, the 4-(2′-pyridyl)phenyl and the 4-(4′-pyridyl)phenyl 4″-n-alkoxybenzoates, have been prepared and their liquid crystal transition temperatures measured. Both homologous series were investigated by differential thermal analysis and the enthalpy changes at the various transitions were measured. Differences in behaviour between the two series are discussed. By comparison of the transition temperatures of certain members of each series with those of corresponding 4-biphenylyl 4″-n-alkoxybenzoates, the order of the effect of the terminal phenyl, and 2- and 4-pyridyl rings in promoting the thermal stability of smectic A and nematic phases has been assessed. The nematic order differs from that reported previously for certain Schiff's bases.