Temperature dependence of Legendre moments in thermotropic liquid crystals

Phase transition temperatures of azomethine esters: 3-hydroxy-4-{[(4-iodophenyl)imino]methyl}phenyl alkanoates (Cn-1H2n-1COO-, n = 8, 18) are identified using Legendre moments or Legendre moment coefficients. As a function of temperature, Liquid crystal textures are recorded from the arthroscopic mode of Polarizing Optical Microscope having the attachment of hot stage and camera. In this paper, Legendre moments are computed from the brightness information of liquid crystal textures using MATLAB software. The changes in the textural features with respect to temperature bring the variations in the brightness values, are useful to identify the phase transitions. The abrupt changes in the Legendre moment curve gives information to understand the transition temperatures of liquid crystals. The obtained results are in good agreement with literature.