Synthesis and Characterization of Liquid Crystalline Behaviour of New Materials Incorporating Two Heterocyclic 1,3,4-Oxadiazole and 1,3,4- Thiadiazole Rings

الملخص

The synthesis and mesomorphic properties of 5-(4-methoxyphenyl)-2-[2-(4'-nalkoxy)-
1,3,4-thiadiazole-5-methylenethio]-1,3,4-oxadiazole (series [VI]n), were described
for the number of the carbon atoms in alkoxy chains varying from 1-8. In addition, four
compounds containing 4'-chloro [VI]a, 4'-nitro [VI]b, 4'-methoxate [VIII]1 and 4'-heptoxate
[VIII]7 instead of 4'-alkoxy group were also synthesized to study the effect of terminal
substituent. All compounds have been characterized by elemental analysis, and FTIR, mass
1HNMR spectrometry. The liquid crystalline properties were investigated by differential
scanning calorimetry (DSC) and optical polarized microscopy (OPM). The homologous with
n=2-4 show enantiotropicnematicmesophase. The higher homologous (n = 5-8) and
compound with 4'-heptaloxate [VIII]7 substituent show enantiotropicnematic and smectic
phases. Finally, the three compounds 4'-chloro [VI]a, 4'-nitro [VI]b, and 4'-metoxate [VIII]1
did not show any mesomorphic properties.