Novel ionic liquid crystals consisting of polyammonium and carboxylate ions were synthesized by ion complexation of polyethyleneimine and carboxylic acids (α,ω-dicarboxylic acids and hydroxyalkanoic acid). Their thermal properties and orientational behavior were examined by polarizing microscopic observation, differential scanning calorimetry, and variable temperature X-ray diffraction measurements. The ionic liquid crystals exhibited thermotropic liquid crystalline phases. The ionic liquid crystals (BP/ndA) bearing counter dicarboxylate ions formed a cubic phase upon heating and cooling. On the other hand, the ionic liquid crystal bearing the counter hydroxyalkanoate ion exhibited enantiotropic smectic A and smectic B phases with focal conic fan textures. These ionic liquid crystalline phases were formed by ionic and hydrophobic interactions because they did not have an aromatic mesogenic group.
Ionic liquid-crystalline materials (ILCMs) with ammonium ions were synthesized. Their thermal and orientational properties were studied by polarizing microscopy, differential scanning calorimetry, and X-ray diffraction (XRD). The ILCMs formed the smectic A phase on heating and cooling. A focal conic fan texture was observed in the phase. In addition, the ILCMs spontaneously formed a perpendicular alignment in the smectic A phase. The XRD patterns of the ILCMs consisted of sharp reflections in the small-angle region and broad band in the wide-angle region in the smectic A phase.
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