Phase studies and thermal stability of binary systems of cholesteric liquid crystals

The binary mixture of cholesteryl oleyl carbonate (COC) and cholesteryl non anoate (CN) with different ratios has been characterized by differential sc anning calorimetry (DSC) to determine the phase diagrams. Their normal shel f-life and accelerated stability studies were also examined. A novel micros copic Fourier-transform infrared (FT-IR) spectrometer equipped with DSC was also used to measure simultaneously the chemical structural variation and the thermal response of these liquid crystals. The results indicate that th e binary mixture might transform from smectic to cholesteric and then to is otropic liquid (CN composition < 50%); from solid to cholesteric and then t o isotropic liquid (CN composition > 50%). Therefore, the 50% CN compositio n might play a critical role in the phase transition of the binary COC-CN m ixture. The microscopic FT-IR/DSC system could also confirm the phase trans ition, but could measure the phase trasition temperature of liquid crystals more easily and sharply than the DSC method. The long-term accelerated the rmal stability of the COC-CN mixture seemed to be more constant when stored at 4 degrees C than in any other temperature conditions.