Abstract

A homologous series of liquid crystal bearing with heterocyclic thiophene Schiff base ester with alkanoyloxy chain (CH3(CH2)nCOO–, where n=4, 6, 8, 10, 12, 14, 16) was successfully synthesized through the modification of some reported methods. The structural information of these compounds was isolated and characterized through some spectroscopic techniques, such as FTIR, 1H, and 13C NMR and elemental analysis. Textural observation was carried out using a polarizing optical microscope (POM) over heating and cooling cycles. It was found that all synthesized compounds (3a–g) exhibited an enantiotropic nematic phase upon the heating and cooling cycle with high thermal stability. Moreover, a characteristic bar transition texture was observed for compounds 3f and 3g which have shown transition of nematic-to-smectic C phase. This has been further confirmed by obtaining relative phase transition temperature using the differential scanning calorimetry (DSC).

Highlights

  • The design and investigation of new mesogens are fast garnering interest from liquid crystal researchers [1]

  • Thermotropic liquid crystalline compounds possess a number of unique properties that are of immense value

  • All of the synthesized compounds showed the presence of a single spot in thin layer chromatography (TLC) plates

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Summary

Introduction

The design and investigation of new mesogens are fast garnering interest from liquid crystal researchers [1]. New mesogens with heterocyclic compounds such as benzothiazole [6, 8, 9], benzoxazole [10], 1,2,4-oxadiazole [11], pyrimidine [12], and pyrazole [13] had attracted the interest of scientists, as the insertion of heteroatom will strongly influence the formation of mesomorphic phases. These heterocyclic structures generally incorporate unsaturated atoms, such as O, N, or S, and due to the high electronegativity of these atoms, it often results in reduced symmetry of the molecules and creates a stronger polar induction. The derivatives possess three core units (one thiophene and two phenyl rings) and are connected via a Schiff base and ester linkers, which increases both the molecular broadness and anisotropy

Experimental
Results and Discussion
Conclusion

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