Characterization of Two Isomeric Cyano-Ester Homologous Series — I

Abstract

Current theories concerning the incidence of the reentrant nematic phase in liquid crystals generally incorporate the extent to which the molecules are paired in the nematic phase as a basis for the occurence of reentrant phenomenon. In this study we sought to prepare materials in which the dipolar forces within the constituent molecules could be altered and hence, the degree of pairing in the nematic phase could be changed. Thus, a comparison of the properties of the 4-cyanophenyl 4’-n-alkoxybenzoates with those of the 4-n-alkoxyphenyl 4’-cyanobenzoates was made. It was found that the latter series exhibited unusual properties; an injection of smectic C phases and dual crystalline forms which melted at different temperatures. Indeed, the injection of smectic C properties into the series appears to indicate that the pairing is so strong that the reentrant phase gives way to smectic C formation; this formation in itself is unusual when observed for cyano compounds.