Thermodynamic and Viscometric Studies on the Thermotropic Phase-Stability of Cholesteryl Myristate, Palmitate, Stearate, and Oleate

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By means of differential scanning calorimetry and polarizing microscopy, the transition paths, temperatures, enthalpies and isopiestic heat capacities were measured for four mesogenic esters, i.e. cholesteryl myristate (ChM), palmitate (ChP), stearate (ChS), and oleate (ChO). By using the above-mentioned thermodynamic quantities, relative chemical potential diagrams were constructed to clarify the thermodynamic phase stability of each ester. The viscosity behavior of each ester was measured at various temperatures under various conditions : continuous heating and cooling as well as isothermal. The effect of thermal history before the isothermal measurements was also examined. On the basis of chemical potential and viscometric diagrams, the phase stability of each ester with or without the influence of shear in the viscometer is discussed. Each ester in cholesteric phase was estimated to behave as a "continuum" without shear, but as a "swarm" under shear. The nature of the peak or hump in the transtion region between isotropic and cholesteric phases is also discussed.
社団法人日本薬学会の論文
1986-07-25