Effect of Solvent Type on the Thermodynamic Properties of Normal Aliphatic Cholesteryl Esters

Abstract

The effects of purity on the phase transitions in cholesteryl esters have been observed by several workers (1, 2, 3). In addition, recent calorimetric studies have indicated that cholesteryl esters have more than one stable room temperature solid form (3). Barrall, Porter and Johnson found that for certain esters the transition temperature of the solid→mesophase conversion was very sensitive to the way in which the solid phase had been formed, from ethanolic solution or from the melt (3). Indeed, the propionate ester exhibited two overlapping endotherms for the solid→mesophase transition when the solid had been formed from the melt. The same solid formed from ethanolic solution exhibited only one endotherm. These and other reported effects indicate that the esters of cholesterol have an extensive solid-phase polymorphism.

Part XX of a Series on Order and Flow of Liquid Crystals