Influence of Hydrogen Bonding Interactions Between New Pyridine Derivatives and 4-N-Alkyloxybenzoic Acids on Mesomorphism

The fascinating supramolecular structures formed through intermolecular hydrogen bonding (HB) interactions gain importance in the research of materials and biological sciences. Pyridine-infused molecular units are more prone to form HB interactions with other moieties like carboxylic acids, alcohols, thiols etc. The high thermal span of mesomorphism, low melting and clearing temperatures, appropriate dielectric and bi-refringence anisotropy, high spontaneous polarization, low threshold voltage, low switching times etc. are some of the important properties required for technical appli-cations of liquid crystalline materials. Chemists mainly focus on design and synthesis of new materials with device desired properties. In this study, an attempt has been made to develop new mesomorphic materials with large thermal span and towards ambient temperatures through Hydrogen bonding interactions. New pyridine deriva-tives of Schiff’s base with dihalo substituents are prepared and are used to form the in-termolecular HB interactions with 4-n-alkyloxybenzoic acids (nOBAs). The 4-n-alkyloxybenzoic acids (nOBAs) are inherently mesomorphic whereas the new pyridine derivatives are non-mesogenic. The 1:1 binary mixtures of pyridine derivatives and nOBAs are found to involve HB interactions and the inherent mesomorphism of nOBAs is varied. The nematic and smectic-C mesophases of nOBAs are quenched and smectic-A mesophase is induced towards the ambient temperatures. The infrared spectroscopy is used to ascertain the intermolecular HB interactions, polarizing optical microscope (POM) in conjunction with a temperature controller and differential scan-ning calorimeter (DSC) are used to ascertain the mesomorphism and phase transition temperatures respectively. The mesomorphic thermal spans are found to be enhanced in present studies as the chain length of carboxylic acids increases.