Author: Padmavathi Sariki, Vasundhara Balireddy, Sankara Rao Gowri B. and Ratna Raju M.

DOI: http://doi.org/10.31788/RJC.2023.1628236

The refractive index of liquid crystals at infrared wavelengths is to be measured using a novel technique. This method involves constructing the envelopes for the transmitted intensities using the envelope method on Fourier transform infrared spectral data before doing refractive index measurements. The upper and lower envelopes for the envelope approach are made using the transmitted wavenumber intensities. In this case, we consider hydrogenbonded mesogens, specifically p-n-alkyl benzoic acid : p-(p'-Octyloxybenzylidene)-p-cyanoaniline (nBA: OBCA, where n=6, 8). The outcomes of this research demonstrate that the hydrogen-bonded mesogens nBA:OBCA have higher refractive indices than the pure compounds. Refractive index values in the infrared area drop with decreasing wave number and reach saturation. The proposed technique evaluates samples' refractive indices in the infrared region (4000cm-1 - 400cm-1) which is difficult-to-measure. Molecular interactions of hydrogen-bonded liquid crystals are also investigated.

Keywords: Fourier Transform Infrared Spectroscopy, Liquid Crystals, Hydrogen bonds, Envelopes, Refractive Index.