Analysis of optical and thermal properties of double hydrogen bonded liquid crystal binary mixtures

ABSTRACT

Eighteen binary mixtures are prepared from three thermotropic double hydrogen bonded liquid crystal complexes formed by Mesaconic Acid (ME) and various alkyloxy benzoic acids, namely ME + 5BAO, ME + 11BAO and ME + 12BAO where 5BAO, 11BAO and 12BAO represents pentyloxy benzoic acid, undecyloxy benzoic acid and dodecyloxy benzoic acid respectively. Two sets of binary mixtures (ME + 12BAO with ME + 5BAO and ME + 11BAO with ME + 5BAO) are formed by varying their molar ratio in steps of 0.1 to 0.9 which leads to the formation of eighteen binary mixture complexes. Existence of different energy bands in the binary mixtures is identified from the analysis of Fourier Transform Infrared Spectroscopy (FTIR). Phases such as nematic and smectic C are observed in all the binary mixtures which are confirmed through Polarizing Optical Microscopy (POM). Transition temperatures corresponding to the individual mesophases are further verified using Differential Scanning Calorimetry (DSC). Phase diagram of two sets of binary mixtures are constructed with the aid of POM and DSC data. Optical tilt angle measurement; a primary order parameter; is calculated in smectic C phase of the binary mixtures and the resultant data obtained is fitted to critical exponent value is in concurrence with the Mean Field theory predicted value. Thermal studies such as stability factor, order of phase transitions and specific heat capacity value of the mesophases are extracted from the DSC thermograms.

KEYWORDS:

• Binary mixtures
• double hydrogen bonded liquid crystals
• optical tilt angle
• specific heat
• stability factor

Acknowledgements

Bannari Amman blessings and Infrastructural support provided by Bannari Amman Institute of Technology are acknowledged gratefully.