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Two homologous series of calamitic liquid crystals containing a benzothiazole ring and two different linkages have been prepared, and their liquid crystalline properties are studied and compared with each other and those of similar structure. The mesogens with only the cinnamate linking group showed better thermal properties than those with an ester. Nematic and smectic phases were observed. All the compounds of both the series were characterized by elemental analysis, FT-IR, mass spectrometry,1H-NMR, and13C-NMR. Phase transition temperatures and the thermal parameters were obtained from differential scanning calorimetery (DSC). The textural observations were performed using hot-stage Polarizing Optical Microscopy (POM). [ABSTRACT FROM PUBLISHER]

Two new mesogenic homologous series of Schiff base esters, 2-[4-(4′-n-Alkoxy benzoyloxy) benzylidenamino] 3-cyno thiophine (Series-A) and Schiff base cinnamates, 2-[4-(4′-n-alkoxy cinnamoyloxy) benzylidenamino] 3-cyano thiophene (Series-B), comprising a thiophene moiety were synthesized. Structural elucidation was carried out using elemental analysis and spectroscopic techniques such as FT-IR, 1H-NMR and 13C-NMR, and mass spectrometry. The mesomorphic properties and thermal stabilities of the title compounds were studied by using differential scanning calorimetry and optical polarizing microscopy. All the derivatives are mesomorphic in nature showing the nematic phase, and the higher members of Series-A show a smectic C phase whereas Series-B exhibits only the nematic mesophase. The mesomorphic properties of the present series are compared with other structurally related compounds. [ABSTRACT FROM AUTHOR]