Synthesis and mesomorphic properties of novel three-armed star-shaped mesogens of phloroglucinol (1,3,5-trihydroxybenzene) containing Schiff-base moiety

Abstract

A series of symmetrical three-armed star-shaped mesogens based on phloroglucinol (1,3,5-trihydroxybenzene) as a core unit containing (4-benzylidene-substituted-aniline-4′-oxy)-6-bromohexane as peripheral arm where the 4-position at one end consisting different terminal substituent, X (X = fluoro, chloro, bromo, iodo and ethyl) was synthesized and characterized. The chemical structure of the title compounds were studied using FT-IR, ¹H- and ¹³C-NMR while their thermal behavior and mesomorphic properties were investigated via differential scanning calorimetry (DSC) and polarizing optical microscopy (POM). The results indicate that the three-armed compounds containing F, Cl, Br, and C₂H₅ substituents exhibit mesophase except for the analog having iodo substituent which is found to be non-mesogenic. The absence of liquid crystalline properties for iodo-substituted analog could be due to the influence of the substituent of which the lamellar packing of these compounds will be disrupted when the size of substituent is increased.

Keywords:

• star-shaped mesogens
• phloroglucinol
• (4-benzylidene-substituted-aniline-4′-oxy)-6-bromohexane
• mesomorphic

Acknowledgments

G-Y. Yeap would like to thank Universiti Sains Malaysia for the RU Grant No. 1001/PKIMIA/811159. Y-H. Ooi would like to acknowledge Ministry of Higher Education Malaysia (MOHE) for the scholarship (research assistantship).