Legendre Wavelet Transform for the Study of Phase Transitions in Hydrogen-Bonded Liquid Crystals

• Published in: Brazilian journal of physics 2022-12, Vol.52 (6), Article 210
• Main Authors: Sariki, Padmavathi, Balireddy, Vasundhara, B, Gowri Sankara Rao, M, Ratna Raju
• Format: Article
• Language: English
• Subjects: Aniline; Benzoic acid; Computation; Condensed Matter; Crystals; Hydrogen; Hydrogen bonding; Liquid crystals; Liquid phases; Optical microscopes; Phase transitions; Physics; Physics and Astronomy; Software; Texture; Wavelet analysis; Wavelet transforms
• ISSN: 0103-9733; 1678-4448
• DOI: 10.1007/s13538-022-01212-6

In this paper, Legendre wavelet transform–based texture analysis is proposed to study the phase transitional characteristics of hydrogen-bonded liquid crystals. Optical textures are the essential features of liquid crystals and analysis of these textural features is useful to investigate the material characteristics. Hydrogen-bonded liquid crystals: alkyl benzoic acid: p-(p′ -Octyloxybenzylidene)-p-cyano aniline ( n BA:OBCA, n  = 6, 7, 8) are considered for investigation. Intermolecular interactions between the mesogen p-n- alkyl benzoic acid ( n BA) and mesogenic compound p-(p′ -Octyloxybenzylidene)- p -cyano aniline (OBCA) yield the hydrogen-bonded liquid crystals n BA:OBCA. Here, Legendre moments are computed from the wavelet-transformed optical texture using MATLAB computational tool. As a function of temperature, the phase transformations of liquid crystal from crystalline phase to isotropic liquid phase and vice versa can be observed as series of liquid crystal textures using polarizing optical microscope. All these textures show some variations in their features with respect to temperature and most of these variations can be observed as sudden or abnormal changes in transmitted intensity values of textures. They influence the moment values which are computed from the gray level transmitted intensities. Legendre wavelet transform captures the texture information in both frequency and spatial domains. And analysis of this information is useful to study phase behavior of liquid crystals. The results of the proposed methodology are in good agreement with thermal techniques available in the literature.