Synthesis of new schiff base ester liquid crystals with a benzothiazole core

Abstract

A series of new calamitic liquid crystals, 6-methoxy-2-(4-alkanoyloxybenzylidenamino)benzothiazoles, comprising a benzothiazole core, terminal methoxy group and a Schiff base linkage were synthesised and characterised. This series comprises 12 members wherein members differ by the length of the alkanoyloxy chain (C _n-1H_2n-1COO-, where n = 2–8, 10, 12, 14, 16, 18). Their mesomorphic properties were studied by using differential scanning calorimetry, optical polarising microscopy and powder X-ray diffraction techniques. The short chain derivatives (n = 2 and 3) were non-mesogenic compounds, while an enantiotropic nematic phase was present throughout the remaining members of the series. The smectic C phase emerged from the decanoyloxy derivative onwards.

Keywords:

• 6-methoxy-2-(4-alkanoyloxybenzylidenamino)benzothiazole
• Schiff bases
• nematic
• smectic C

Acknowledgements

S.T. Ha would like to thank Universiti Tunku Abdul Rahman (UTAR) for the UTAR Research Fund (Vote No. 6200/H02) 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 and teaching assistantships. The powder XRD measurements were supported by beamline BL17A (charged by Dr Jey-Jau Lee) of the National Synchrotron Radiation Research Center, Taiwan.