Mesomorphic behaviors of a series of heterocyclic benzothiazole-imine-ester-based liquid crystals

A series of new calamitic liquid crystals, 2-[4-(4-alkoxybenzoyloxy) benzylidenamino]benzothiazoles comprising a heterocyclic (benzothiazole) and two phenyl rings core system, terminal alkoxy chain, imine and ester linkers were prepared and characterized. This series comprises eight members wherein the members vary by the length of alkoxy chain (CnH2n+1O-, where n = 4, 6, 8, 10, 12, 14, 16, 18). Spectral analysis results were in conformity with the expected structure. Their thermotropic behaviors were studied by using differential scanning calorimetry, optical polarizing microscopy and powder X-ray diffraction techniques. A single mesophase (nematic) was observed for the first member of the series (n = 4). As the alkoxy chain increased to n = 6, 8, 10, 12, 14, the nematic phase appeared together with an additional SmA phase. When moving from n = 16 until the highest member (n = 18), the nematic phase disappeared and these compounds only exhibited a single mesophase (SmA).