Synthesis, characterization of new carboxylic acid derivatives bearing 1,3,4-thiadiazole moiety and study their liquid crystalline behaviors

ABSTRACT

Thirteen carboxylic acid derivatives containing 1,3,4-thiadiazole ring in their core and swinging alkoxy terminal were synthesized. They were characterized by ¹H, ¹³C NMR spectroscopy, FTIR, and mass spectrometry. Their liquid crystalline behaviors have been studied by differential scanning calorimetry (DSC) and polarized optical microscopy (POM). The 1,3,4-thiadiazole compounds in this study were 2,5 di-substituted asymmetrical, alkoxy, and carboxy linkages. The compounds with alkoxy of long carbon chains (n > 7) displayed Smectic C phase. The liquid crystal properties were found to be affected by the length of alkoxy chain attached to the phenyl moiety and the two types of the dimeric form were resulted from the hydrogen bonding interaction between carboxylic acid molecules.

KEYWORDS:

• 1,3,4-Thiadiazole mesogens
• carboxylic acids
• dimers
• liquid crystals

Acknowledgments

The authors are grateful to the staff of chemistry department in Al-Mustansiriyah University (Baghdad, Iraq) for their help and cooperation's with us. Also many thank to Dr. Mohanad H. Masad (Al al-Bayt University, Jordan) and Dr. Dhafir Al-Heetimi (Baghdad University) for their help us in carrying out ¹HNMR and DSC analysis, respectively. We are indebted to ASTF (Arab Science of Technology Foundation), for their generous support by providing us with optical polarizing microscope (OPM) and hot-stage.