Chiral liquid-crystalline polyesters. Structural effects on mesomorphic behaviour

Abstract

Thermotropic liquid-crystalline polyesters based on mesogenic aromatic residues and intrinsically non-mesogenic chiral segments are described, and an analysis of the thermal and optical behaviour in the bulk and of the chiroptical properties in dilute solutions is presented.

The polymers of interest comprise two major classes according to the nature of the diacid and dihydroxy component. Bipolyesters and cobipolyesters based on the (R)-3-methyladipyl residue and several dihydroxy aromatic mesogens belong to the first class, and in the second class are included polyesters derived from mesogenic bis(4-carboxyphenyl)terephthalate itself or mixtures with isophthalate or phthalate isomers and various symmetric or non-symmetric chiral diols.

Structural effects on the properties in the bulk and in solutions are discussed. In particular, the nature of the different mesogenic groups and the structure and optical purity of the chiral component (diol or diacid), as well as the chemical composition and monomeric unit distribution, are considered. Convenient routes to the synthesis of mesomorphic polyesters with modulated thermotropic properties relevant to the onset, nature and breadth of the mesophase are indicated.