Phase Transition Studies In P-Pentyl Benzoic ...

Phase Transition Studies In P-Pentyl Benzoic Acid:P- Butyl Hydroxy Benzoate (5ba:Bhb) Liquid Crystal

Author Name : S. V. Kumara Sastry, C. Uma Devi, S. Sreehari Sastry

ABSTRACT

Supramolecule p – pentyl benzoic acid: Butyl-p- hydroxy benzoate (5BA: BHB) through hydrogen bond  formation with mesogen containing Supramolecule p–pentyl benzoic acid (5BA) and non mesogen  Butyl-p- hydroxy benzoate (BHB) is synthesized. Newly synthesized compound’s phases and phase transition temperatures are determined by polarizing optical microscope attached with colour high resolution camera and hot stage studies. To confirm the phase transition temperatures differential scanning caloriemeter are carried out.  Hydrogen bond is confirmed through FTIR. The formation of inter molecular hydrogen bonding between COOH group of 5BA and OH group of BHB can be invoked on the basis of hypsochromic shifts in n(C=O)_acid of 5BA (2 cm^-1) and in n(C–O)_Phenolic mode of BHB (16 cm^-1) and a bathochromic shift in n(OH)_phenolic  mode  of BHB (310 cm^-1) in KBr upon complexation which strongly supports the existence of H – bonding. The study reveals that the mesogen 5BA: BHB exhibits enantiotropic induced smectic G phase due to formation of hydrogen bond. The liquid crystalline phase span is more when compared to its counter parts of ethyl/propyl hydroxyl benzoates.

Keywords; Supramolecule, hydrogen bond, Polarizing optical Microscope, Differential Scanning Calorimetry, Fourier Transform Infrared Spectroscopy