Akihiko Takada

Columnar liquid crystals in oligosaccharide derivatives. II. Two types of discotic columnar liquid-crystalline phase of cellobiose alkanoates

Abstract A series of cellobiose octaalkanoates, Cel-II-n (n is the carbon number of the alkyl chain), with n = 7–14 were prepared and their mesogenic properties examined by differential scanning calorimetry, optical polarizing microscopy and X-ray diffraction. All of these compounds form enantiotropic discotic columnar phases, in which the columns are built up by a regular stacking of the cellobiose moieties and are packed in a two dimensional lattice. Homologues with n = 9–14 form the Dho phase only whilst the compound with n = 7 forms the Dro phase. The n = 8 compound forms the Dho phase at higher temperatures and the Dro phase at lower temperatures. Structural parameters obtained from X-ray diffraction studies are presented for both phases.

Discotic columnar liquid crystals in oligosaccharide derivatives III. Anomeric effects on the thermo-mesomorphic properties of cellobiose octa-alkanoates

Abstract The α- and β-anomers of cellobiose octa-alkanoates with purities higher than about 95 per cent were prepared from β-cellobiose by two simple esterification methods. The carbon number n of the acyl substituents ranged from 7 to 10 in both anomers. Both α- and β-anomers exhibited two types of discotic columnar phases (Dho and Dro), depending on n and temperature, but their phase diagrams were appreciably different. Generally, the α-anomers formed more stable mesophases than the β-anomers. In the Dro phase of the β-anomers, the column axis was tilted from the normal to the ‘disks’, while no such tilting was observed in the other phases.