Synthesis and Mesomorphic Properties of 2-(4-Alkyloxyphenyl)benzothiazoles

Abstract

A homologous series of 2-(4-alkyloxyphenyl)benzothiazoles with an even number of carbons in the terminal alkoxyl chain was synthesized and characterized. The structure of the compounds was postulated using elemental analyses, FT-IR, NMR, and mass spectrometry techniques. Their liquid crystalline properties have been investigated by optical polarizing microscopy, DSC, and X-ray diffraction (XRD) techniques. Whilst the n-octyloxy to n-hexadecyloxy derivatives exhibited a monotropic smectic A phase, the n-ethoxy to n-hexyloxy and the n-octadecyloxy derivatives were not mesogenic. The mesomorphic properties of the present series were compared with other structurally related series to establish the chemical structure-mesomorphic properties relationship.

Keywords:

• 2-(4-alkyloxyphenyl)benzothiazole
• heterocycles
• Smectic A
• structure-property relationship

ACKNOWLEDGMENTS

Author S. T. Ha would like to thank Universiti Tunku Abdul Rahman (UTAR) for the research facilities and the Malaysia Toray Science Foundation (UTAR Vote No. 4359/000) for funding this project. T. M. Koh would like to acknowledge UTAR for the award of the research assistantship. The partial financial support from MOSTI via the eSciencefund (Project No. 03-01-05-SF0366) is also essential to make this project complete. The powder XRD measurements are supported by beamline BL17A (charged by Dr. Jey-Jau Lee) of the National Synchrotron Radiation Research Center, Taiwan.

Notes

The values in italics were taken during cooling cycle.

Cr = Crystal; SmA = Smectic A; I = Isotropic liquid.

()*Monotropic value.