Nematic and Smectic a Phases in <i>Ortho</i>-Hydroxy-<i>Para</i>-Hexadecanoyloxbenzylidene-<i>Para</i>-Substituted Anilines

Abstract

Abstract Four Schiff base esters containing the different substituents of R=CN, OH, SH, and NO2 were synthesized, and the physical characterization was carried out along with spectroscopic techniques (FT-IR and NMR). Thermal properties were analyzed by using differential scanning calometry (DSC), and their liquid crystal textures were observed under polarized optical microscope. All compounds thus obtained exhibit mesomorphic properties of which the alignment of molecules are inclined to either nematic, N (R=SH), or smectic, SmA (for R=CN, OH, and NO2). The unidentifiable subphases in crystal region were recorded in all compounds except that with R=OH. The presence of a lateral hydroxyl group has been claimed to contribute to the enhanced molecular ordering, leading to a higher clearing temperature. Keywords: clearing temperaturemolecular ordering ortho-hydroxy-para-hexadecanoyloxybenzylidene-para-substituted anilinesSchiff base estersthermal stability ACKNOWLEDGMENT G.-Y. Yeap thanks the Malaysia government, especially the Ministry of Science, Technology and Innovation (MOSTI) for funding this project through the intensified research in priority area (IRPA) Research Grant Nos. 09-02-05-3211 EA012 and 305/PKIMIA/612923. The assistance given by the Universiti Sains Malaysia, especially research creativity and management office (RCMO), is also vital for the success of this project. This project is partly financed by university science Malaysia (USM) Short-Term Grant No. 304/PKIMIA/634151 and Soka University's Open Research Project for year 2004–2005. S.-T. Ha is grateful to the MOSTI for the National Science Fellowship. Notes Note: Cr, Cr1, Cr2, crystal; SmA, smectic A; N, nematic; I, isotropic.