Thermotropic Liquid Crystalline Glucose Derivatives with Mesogenic side Chains

Abstract

Many glucose derivatives have been studied so far for their liquid crystalline behavior. Penta-O-n-alkanoylglucopyranoses have been reported to form discotic columnar mesophases. Thermotropic liquid crystals of glucose with mesogenic side chains, consisting of a mesogen, an alkyl spacer and a tail, form the subject of this study. The glucose derivatives were prepared by complete esterification of the hydroxyl groups of glucose with the mesogenic side chains. Their characterization was based on the analysis from cross polarizing microscopy, differential thermal calorimetery, wide-angle X-ray diffraction pattern and nuclear magnetic resonance (both ¹³C and ¹H) spectra. Smectic and chiral nematic (cholesteric) phases have been observed in these macromolecules. The effect on the phase behavior of varying the tail length in the side chains of the molecule was studied. The structural arrangement of such molecules has been proposed based on the observations. These are reported here as the first such observations of liquid crystalline phases in completely substituted chiral glucose molecules with mesogenic side chains.