Accurate Method for the Determination of Phase Transitions in Liquid Crystals with Photoacoustic Technique.

A compact Photoacoustic spectrometer (PAS) was fabricated, for the determination of phase transitions in liquid crystals (LCs). Photoacoustic (PA) technique is a powerful tool for the determination of phase transitions in solids, liquids and gasses compared to other techniques like Raman spectroscopy, Newton scattering, NMR & ultrasound studies and DSC. PA signal information is used to investigate the variations in the optical and thermal properties of the materials during phase transitions. The advantage of PA technique is its simplicity in the sample preparation, and its accuracy in the phase transition studies. The instrumentation details and results of phase transition studies on p-pentyloxy benzoic acid (5OBA), N(4-n-hexadcyloxysalicylidene)-2-methylbutyl-4'-amino-cinnamate, 16O(OH)2MBC and N-(4-n-butyloxysalicylidene)-4'-n-Ketylaniline, 4O(OH)5 are presented. The advantages of PA technique are elaborated. [ABSTRACT FROM AUTHOR]