Study the effect of different terminal substituents on the liquid crystalline properties of the new synthesized 1,2,4-oxadiazole derivatives

Abstract

A new series of 4-(5-(p-tolyl)-1,2,4-oxadiazol-3-yl)phenyl substitutedbenzoate, (III_x) incorporating ester linkage with various substituted groups in various positions on the phenyl ring were synthesized and investigated by FT-IR and ¹H-NMR spectroscopies in addition to the CHN analysis, their mesophase behaviors were examined by optical polarized microscopy (OPM) and differential scanning calorimetry (DSC). Only the derivatives that have terminal substituents in the para position showed liquid crystalline properties with a wide range of nematic phase and various textures (Schlieren, thread-like, marble and nematic droplets) both in heating and/or cooling runs. The relationship between nature and position of the substituent groups, central core and ester linkage of these derivatives with their liquid crystalline properties were studied and the results were analyzed, discussed and compared with other mesogenic materials have a chemical composition similar to the compounds prepared in this study.

Graphical Abstract

Keywords:

• 1,2,4-Oxadiazole
• different substituted
• mesomorphic properties
• liquid crystalline materials

Acknowledgments

The authors express gratitude toward the Chemistry Department at Al-Mustansiriyah University to give them all the vital prerequisites for the finishing of this work by supplying the materials and some examination. We additionally thankful toward Dr. Mohanad H. Masad at Al-al-Bayt University in Jordan and Dr. Dhafir Al-Heetimi at University of Baghdad for helping us in 1HNMR, CHN and DSC techniques. Also, a greater thanks and respect to ASTF (Arab Science and Technology Foundation) for providing optical polarizing microscopy connected to hot stage.