Investigation on the thermal and optical properties of hydrogen bonded liquid crystalline complexes formed from hexyloxy benzoic acid and alkyl benzoic acids

Abstract

Seven hydrogen bonded thermotropic liquid crystalline complexes are formed between hexyloxy benzoic acid (6BAO) and p-n-alkyl benzoic acids (nBA, where n refers alkyl carbon chain length which varies from 2 to 8) and characterized. Chemical characterization such as FTIR, ¹H and ¹³C NMR studies are performed to confirm the hydrogen bond existence and chemical environment of the proposed molecular structure respectively. The existence of mesophases such as nematic and smectic F in the synthesized complexes are observed by Polarizing Optical Microscope (POM). The thermal analysis of this series is executed with the aid of Differential Scanning Calorimeter (DSC), which gives clear picture about the phase transition temperatures and their corresponding enthalpy values. Phase diagram is constructed with the help of the data consolidated from POM and DSC. Navard and Cox method have been implemented in estimating the order of phase transition. Specific heat capacity and light filtering action are the additional characterization techniques carried out in this described work.

Keywords:

• light filtering action
• order of transition
• phase transition
• specific heat capacity

Acknowledgements

Eternal blessings of almighty, infrastructural support rendered by Bannari Amman Institute of Technology and NMR facility provided by Madurai Kamaraj University, Madurai, India, are gratefully acknowledged.