The Mesomorphic Behaviour of Bisalkyl 4,4′-(Terephthaloyldioxy)dibenzoates as Models of Thermotropic Polyesters

Abstract

The thermotropic liquid-crystalline behaviour of fifteen bisalkyl 4,4′-(terephthaloyldioxy)dibenzoates, as possible model compounds of corresponding polyesters, was studied by DSC and polarizing microscopy. The flexible tails included linear or branched alkyl groups, aryl alkyl groups, or oxygen-containing groups. Depending on the structure of the flexible tails, smectic A, smectic C, nematic or cholesteric phases were observed. The X-ray diffraction study of the homologues with linear alkyl chains showed the existence of a smectic A phase for alkyl groups constituted by 4 to 8 carbon atoms, and both smectic A and C phases for samples with alkyl tails with 9 and 10 carbon atoms. The influence on the nature of the flexible chains on the thermotropic behaviour of the compounds is discussed, in relation to the behaviour of corresponding structurally analogous polyesters.

Key Words:

• bisalkyl 4,4′-(terephthaloyldioxy)dibenzoate
• smectic phases
• thermotropic polyesters
• model compounds