Abstract
Liquid crystalline Schiff base esters have been synthesized and characterized by the esterification of various aliphatic and aromatic acids with different 4' substituted N-benzylidene 4-hydroxy anilines. The structures of the synthesized compounds were established through elemental analysis, mass spectrometry, Fourrier transform IR, H-1 and C-13-NMR spectroscopy. The IR absorption spectra of all the Schiff bases showed characteristic bands in 3360-3328 cm(-1) range corresponding to the presence of hydroxyl group. The appearance of downfield singlets around 9.63-9.52 ppm (OH and 8.67-8.56 ppm (CH=N) respectively confirmed phenolic and azomethine protons in nmr spectra. The mesomorphic properties were studied using POM, DSC and XRD. The textures developed, enthalpy changes and x-ray diffraction patterns were associated to nematic phase. Consistent with earlier findings (Yeap et al 2006), the palmitoyl Schiff base from EP and EM series form only smectic phase which is believed to be lamellar arrangement. The occurrence of only a broad diffraction at 4.6 angstrom at 150 degrees C in XRD pattern indicated a nematic mesophase for EPMB2.