THERMODYNAMIC STUDY OF BINARY MIXTURES OF LIQUID CRYSTALS CHOLESTERYL MYRISTATE AND DODECYLOXYBENZOIC ACID

Abstract

Transition temperatures, transition enthalpies and transition entropies of the binary mixtures of Cholesteryl Myristate (ChM) and Dodecyloxybenzoic Acid (DDOBA) have been measured at different scanning rates using differential scanning calorimeter (DSC). Different mesophases have been identified by analyzing their textures under the polarizing microscope. Pure component ChM has smectic A (SmA) and cholesteric (N*) whereas DDOBA has smectic C (SmC) and nematic (N) mesophases. Phase diagrams for this binary system have been drawn in both heating and cooling cycles. The eutectic composition of the mixture has been found to be 30±5 mole percent of DDOBA. Stability of SmA phase of ChM increases with the addition of DDOBA upto about 50 mole percent of DDOBA but decreases thereafter and completely disappears at about 78 mole percent of DDOBA. Range of SmC phase of DDOBA (−36°C) decreases rapidly with the addition of ChM and disappears at about 19 mole percent of ChM. The maximum range of N* phase in this binary system is about 27°C in heating and 43°C in cooling. Maximum range of SmA phase in the cooling is about 52°C.

Key Words:

• Binary mixture
• Eutectic
• Cholesteryl Myristate
• Dodecyloxybenzoic Acid
• Thermodynamic