Thermodynamical and Optical Studies of Ternary Mixtures of 4-n-Heptyloxy Benzoic Acid, 4-n-Decyloxy Benzoic Acid, and 5-Cholesten-3ß-ol 3-octanoate

Abstract

Binary eutectic mixture of 4-n-heptyloxybenzoic acid (HOBA) and 4-n-decyloxybenzoic acid (DOBA) shows smectic C (SmC) and nematic (N) phases over a wide temperature range. 5-cholesten-3β-ol 3-octanoate(ChO), which has monotropic chiral nematic (N∗) phase, has been added as third component in the eutectic bi-component mixture (BCM) of HOBA-DOBA in different mole ratios. Transition temperatures and enthalpies of the ternary mixtures have been determined by using differential scanning calorimeter (DSC) and mesophases have been identified with the help of polarizing microscope. It has been observed that the thermal stability of SmC phase of BCM decreases rapidly due to the addition of ChO molecules and SmC phase is completely suppressed for about 10–12 mole percent of ChO. A narrow temperature range TGBC phase has been observed for ChO concentrations 2 to 8 mole percent. For higher concentrations of ChO molecules, TGBA and SmA phases have been induced over a wide temperature range. Ternary system of ChO and BCM shows N∗ phase over a wide temperature range in the heating and cooling cycles at about eutectic composition (12.5 mole percent of ChO) of ChO-BCM system.