Thermal Analysis of Supramolecular Hydrogen-Bonded Liquid Crystals Formed by Nonyloxy and Alkyl Benzoic Acids

Abstract

A novel series of supramolecular hydrogen-bonded complexes (supramolecular hydrogen-bonded liquid crystal, SMHBLC) has been isolated from equimolar ratios of p-n-nonyloxy benzoic acid (9BAO) and seven p-n-alkyl benzoic acids (nBA) whose carbon number varied from ethyl to octyl. Complementary hydrogen bonds are formed between them. They have been investigated by polarizing optical microscopy (POM), differential scanning calorimetry (DSC) and further these data are utilized for the construction of phase diagram. Characteristic textures of the orthogonal and tilted phases have been recorded and compared. A new smectic ordering referred to as smectic X is characterized by various techniques. Odd–even effects are evinced in transition temperatures. The order of the transitions is distinguished by thermal analysis. The magnitude of experimental optical tilt angle in smectic C of all the homologs is fitted to a power law and the value of exponent is found to concur with the mean field theory predicted value.

Keywords:

• Hydrogen-bonded liquid crystals
• odd–even effect
• optical tilt angle
• smectic X
• thermal analysis

Acknowledgments

The divine blessings of almighty Bannari Amman, the infrastructural support rendered by Bannari Amman Institute of Technology, and the financial support rendered by the Board of Research in Nuclear Sciences (BRNS) of Department of Atomic Energy (DAE), India (sanction no. 2012/34/35/BRNS) are gratefully acknowledged by the authors.