| dc.description.abstract | Abstract
Numerous known examples of hydrocarbon structures, used as core groups exhibiting columnar phases have been reported. However, examples of heterocyclic structures used as core groups are relatively less. The presence of nitrogen, sulfur or oxygen atoms on these heterocyclic rings, which likely introduce a transverse dipole moment often resulted in a change in dielectric anisotropy. The formation of liquid crystallinity in such heterocyclic compounds might be facilitated by weak p - p interaction between these aromatic or heterocyclic rings.
In this work a new type of heterocyclic compounds, 4-alkoxybenzoic acid 4-(6-alkoxy benzoxazol-2-yl)phenyl esters, in which an unsaturated benzoxazole ring was utilized as the rigid core group, were prepared and their mesomorphic properties studied. All compounds were characterized by 1H-, 13C-NMR spectroscopy, powder X-ray diffraction and the mesomorphic properties of these compounds were studied by DSC analysis, optical polarized microscope and powder XRD diffraction. The results indicated that these rod-like compounds exhibited nematic (N) and smectic (SmC) phases. The range of mesophase temperatures was slightly dependent on the ratio of width-to-length (d/l, i.e., aspect ratio) of the molecular shape. | en_US |