Phase diagram of bicomponent mixtures of liquid crystals: Cholesteryl myristate and decyloxybenzoic acid

Abstract

Mixtures of two different liquid crystals (LCs) have been used to formulate a technologically viable LC operating at room temperature. Cholesteryl myristate (ChM) and decyloxybenzoic acid (DOBA) have been mixed in different molar ratios. Pure DOBA exhibits smectic C (SmC) and nematic (N) mesophases while pure ChM shows smectic A (SmA) and cholesteric (N*) mesophases. Transition temperatures have been determined using differential scanning calorimetry. Phase identification has been done using optical polarizing microscopy. Phase diagram shows the eutectic composition of ChM-DOBA system in the ratio 70:30 mole %. In this system, as the addition of DOBA is increased, stability of SmA phase of ChM increases up to 56 mole % of DOBA but as the addition of DOBA increases from 56 mole %, stability of SmA phase of ChM decreases and completely vanishes at about 80 mole % of DOBA. Range of SmC phase of DOBA (approximately 23°C) decreases rapidly with the addition of ChM and disappears at about 15 mole % of ChM. The maximum range of cholesteric (N*) phase in the binary system as observed in the heating cycle is about 24°C.