Design synthesis and characterization of binary hydrogen bonded liquid crystalline homologous series

Abstract

Liquid crystals (LC) are having the properties between isotropic liquid and crystalline solids. They are flowing like fluid but possess degree of ordering. In addition to that they are having the physical properties such as refractive index, dielectric constant, conductivity and elastic constant etc., Liquid crystals are generally classified as thermotropic, lyotropic and metallotropic mesogens. Due to the dynamic properties of thermotropic liquid crystals, it has more advantages than other types of liquid crystals. Intermolecular hydrogen bonds play an important role to assemble the molecules in the LCs. So the formation of inter molecular hydrogen bonds between the molecules induces the mesogenic properties due to the presence of reactive site of the organic compounds. Thus, the hydrogen bonded liquid crystals (HBLCs) brings more awareness among the LC researchers due to the induced new mesogenic phases and considerable applications in the different fields.A series of H-bonded LCs are synthesized from the combination of mesogenic and nonmesogenic carboxylic acids. The obtained mesogenic complexes are characterized using different techniques to analyze their distinctive physical and chemical properties. Molecular interaction between 4- methoxycinnamic acid and p-n-alkyloxy benzoic acids (nOBA, where n=3 to 12) is studied. As a result the hydrogen bonded binary liquid crystal complexes are prepared by the well documented synthetic route. The synthesized HBLC complexes are characterized by the optical and thermal analysis and the observed textures are compared with reported literatures. Transition temperature, enthalpy values of individual mesogenic phases and its order of transitions are identified using differential scanning calorimetry newline