Research Article Open Access

New Mesogenic Schiff Base Esters with Polar Chloro Substituent: Synthesis, Thermotropic Properties and X-Ray Diffraction Studies

Sie-Tiong Ha1, Lay-Khoon Ong1, Yasodha Sivasothy1, Guan-Yeow Yeap1, Peng-Lim Boey1 and Hong-Cheu Lin1
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American Journal of Applied Sciences
Volume 7 No. 2, 2010, 214-220

DOI: https://doi.org/10.3844/ajassp.2010.214.220

Submitted On: 7 February 2010 Published On: 28 February 2010

How to Cite: Ha, S., Ong, L., Sivasothy, Y., Yeap, G., Boey, P. & Lin, H. (2010). New Mesogenic Schiff Base Esters with Polar Chloro Substituent: Synthesis, Thermotropic Properties and X-Ray Diffraction Studies. American Journal of Applied Sciences, 7(2), 214-220. https://doi.org/10.3844/ajassp.2010.214.220

Abstract

Problem statement: Many studies have been conducted on the Schiff base’s alkyl and alkyloxy possessing terminal halogen substituent. However, the thermotropic properties of Schiff base’s ester (or alkanoyloxy) with chloro terminal group remained unstudied. Approach: Synthesis a series of new Schiff base ester possessing polar chloro group and investigate its mesomorphic properties. The title compounds were prepared via condensation and esterification reactions. The molecular structures were confirmed using spectroscopic techniques. All the members are differed by the length of alkanoyloxy chain, Cn-1H2n-1COO, where n = 2-8, 10, 12, 14, 16 and 18. The mesomorphic properties were studied using differential scanning calorimetry, polarizing optical microscopy and temperature-dependent X-ray diffractometry. Results: Whilst short members (n = 2-5) were not mesogenic compounds, n-hexanoyloxy and n-heptanoyloxy derivatives exhibited monotropic SmA and SmB phases. Enantiotropic smectogenic A and monotropic smectogenic B were observed in n-octanoyloxy to n-hexadecanoyloxy derivatives. Highest member of the series, n-octadecanoyloxy derivatives exhibited monotropic SmA phase. Conclusion: The ester linkage and polar terminal group in the present series are essential for the formation of liquid crystal phase in Schiff bases.

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Keywords

  • Azomethine
  • liquid crystal
  • smectic A
  • smectic B
  • X-ray diffraction