The Effect of Alkanes as Solutes on the Transition Temperatures of Liquid Crystal Substances : Cholesteryl Myristate and Cholesteryl Palmitate

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Transition temperatures between coexisting (solid-smectic, solid-cholesteric, smectic-cholesteric and cholesteric-isotropic liquid phases) of cholesteryl myristate (ChM) and cholesteryl palmitate (ChP) were studied by differential scanning calorimetry (DSC) as well as polarized light microscopy, in the presence and absence of n-heptane, n-octane and n-nonane as solutes. The polymorphism of ChM and ChP was maintained in spite of the addition of ca. 0.06 molar ratio of alkanes, although the distinction between coexisting phases decreased in enthalpy and entropy terms, resulting in the disappearance of liquid crystal phases (smectic and cholesteric phases). The addition of alkanes markedly depressed the transition temperatures ; this could be described quantitatively by thermodynamic analysis, taking into consideration the partition of alkanes between coexisting phases. The partition coefficients and the molar transition excess enthalpies of alkanes on mixing with ChM and ChP were calculated by simulation. The partition coefficients obtained from the DSC study agreed reasonably well with those previously determined by gas-liquid chromatography.
社団法人日本薬学会の論文
1979-06-25