Chiral Mesophases of 12-Hydroxyoctadecanoic Acid in Jelly and in the Solid State. II. A New Type of Mesomorphic Solid State

Abstract

A new type of chiral solid mesophase was obtained by evaporating the solvents from solutions or jellies of chiral 12-hydroxyoctadecanoic acid (12HOA). The mesomorphic solids exhibited some optical properties characteristic of a helicoidal mesophase: (1) spherulitic or Schlieren texture under a polarizing microscope, (2) reflective circular dichroic band, and (3) induced circular dichroic spectra with a single sign due to achiral molecules added to the solid. From the circular dichroic and X-ray studies, it was concluded that the helicoidal mesophase structure exists locally as small domains with a chiral smectic structure within the mesomorphic solids. Microscopic observation revealed that, upon heating, the transition of the mesomorphic solid to the crystalline solid occurred. This process was studied by differential scanning calorimetry. Formation of a variety of helicoidal systems from chiral molecules such as 12HOA and polypeptides was regarded as a phenomenon characteristic of chiral assemblies of amphiphilic molecules.