عنوان المقالة:New mesogenic materials bearing 1,2,4- oxadiazole moiety: Synthesis, characterization and investigation their mesomorphic behaviors New mesogenic materials bearing 1,2,4- oxadiazole moiety: Synthesis, characterization and investigation their mesomorphic behaviors
ABSTRACT
In this work, two series containing a 1,2,4-oxadiazole ring as a central core were synthesized and
characterized by common spectroscopic techniques, including FT-IR, 1
H-NMR, and elemental
analysis. The first series was 3-(4-alkoxyphenyl)-5-(p-methylphenyl)-1,2,4-oxadiazole (Cn), which
consisted of alkoxy group in the terminal arm and a methyl group in the other, while, the
oxidation reaction of methyl group in a series (Cn) to the carboxy group was the method used
to synthesize the second series in this work, 4-(3-(4-alkoxyphenyl)-1,2,4-oxadiazol-5-yl)benzoic
acid (Dn). The mesophase behaviors of these two series were studied by optical polarized
microscopy (OPM) and differential scanning calorimetry (DSC). The liquid crystalline investigations
of the compounds (Cn and Dn) show that the last six homologeus of the series (Cn), (C6–C11), have
a monotropic nematic phase, while only the intermediate compounds in the series (Dn), (D3–D9),
displayed monotropic nematic phase, also, the liquid crystalline properties in the first and last two
compounds in this series (D1, D2, D10, and D11) had disappeared. The differences in liquid
crystalline properties between the two series, (Cn and Dn), were discussed through the influences
of the different terminal groups (–CH3 and –COOH) in addition to the effect of the 1,2,4-oxadiazole
ring and the length of the terminal alkyl chain.
غسان قيس علي | Ghassan Qays Ali | 5056