The Mesomorphic Behavior of S-Cholesteryl ω-Phenylalkanethioates

Abstract The first 16 homologous S-cholesteryl ω-phenylalkanethioates were synthesized from 3β-mercaptocholest-5-ene and the imidazolides of the corresponding ω-phenylalkanoic acids. The mesomorphic properties of these compounds were determined by microscopic inspection and by differential scanning calorimetry. With the exception of the phenylthioacetate, the 4-phenylbutanethioate, and the 6-phenylhexanethioate, all homologs are cholesteric. S-Cholesteryl 8-phenyloctanethioate and its higher homologs are monotropic smectic. Both the cholesteric-isotropic and the smectic-cholesteric transition temperatures fall on two hyperbolic curves: a high temperature branch for homologs of odd and a low temperature branch for homologs of even acyl chain length. Some of the cholesteric members, of this series exhibit the visible spectrum of selectively reflected light within a narrow temperature range.