Thermal and mesomorphic behavior of hydrogen-bonded liquid crystals of new pyridine derivatives

The fascinating supramolecular structures formed through intermolecular hydrogen bonding (HB) interactions have gained importance in materials and biological science research. Pyridine-infused molecular units are more prone to form HB interactions with other moieties, such as carboxylic acids, alcohols, and thiols. In this study, new mesomorphic materials with large thermal spans and towards ambient temperatures were synthesized through hydrogen bonding interactions. New pyridine derivative of Schiff’s base with dihalo substituents was prepared and used to form intermolecular HB interactions with 4-n-alkyloxybenzoic acids (nOBAs). The 4-n-alkyloxybenzoic acids (nOBAs) are inherently mesomorphic, whereas the new pyridine derivative is non-mesogenic. The 1:1 binary mixtures of pyridine derivative and nOBAs were found to involve HB interactions, and the inherent mesomorphism of the nOBAs varied. The nematic and smectic-C mesophases of nOBAs are quenched, and the smectic-A mesophase is induced at ambient temperatures. Infrared spectroscopy was used to ascertain the intermolecular HB interactions and polarizing optical microscopy (POM) in conjunction with a temperature controller and differential scanning calorimetry (DSC) were used to ascertain the mesomorphism and phase transition temperatures, respectively. The mesomorphic thermal spans were found to be stabilized in the present study as the chain length of carboxylic acids increased. The melting and clearing temperatures of the complexes were lower than those of the nOBAs.