Trends in the nematic–isotropic liquid transition temperatures for the homologous series of 4-n-alkoxy- and 4-n-alkyl-4′-cyanobiphenyls

Abstract

The lower homologues of the series of 4-n-alkoxy- and 4-n-alkyl-4′-cyanobiphenyls have been prepared and their liquid crystal transition temperatures determined. The trends in the nematic–isotropic liquid (N–I) transition temperatures along the series are compared with observed trends for other homologous series. These results reveal deficiencies in the theoretical treatments that have been proposed to explain trends in N–I transition temperatures in such series. However, the results may be explained by the existence, in the case of the higher homologues, of certain alkyl chain conformations which are especially favourable to the stability of the nematic phase