THERMOPHYSICAL PROPERTIES OF CHOLESTERYL OLEYL CARBONATE DETERMINED WITH MICROSCOPIC FTIR DSC SYSTEM/

A microscopic Fourier transform infrared spectrometer (Micro FTIR) equ ipped for differential scanning calorimetry (DSC) was used to measure simultaneously the chemical structural variation and the thermal respo nse of phase transition of cholesteryl oleyl carbonate (COC). The diff erential scanning calorimeter served also to determine the phase trans itions of COC during heating or cooling. Two endothermic features due to phase transition were found in the thermogram: 18.3 degrees C for a smectic-cholesteric transition and 37.5 degrees C for a cholesteric-i sotropic transition during heating; 35.1 degrees C for an isotropic-ch olesteric transition and 15.8 degrees C for a cholesteric-smectic tran sition during cooling. The breadth of the feature indicated sluggish p hase transitions. The three-dimensional plot indicated that the intens ities of lines due to the C-H stretching and scissoring deformation mo des and C=O stretching mode of COC decreased suddenly near the tempera ture of phase transition during heating but the intensity of the line dues to the C-O stretching mode of carbonate ester of COC increased. L attice vibrations or coupling of vibrational modes might be responsibl e for the result. These intensities in the cooling process varied inve rsely to those in heating process.