Synthesis and phase transition behavior of calamitic liquid crystals containing heterocyclic core and lateral ethoxy substituent
A series of new calamitic liquid crystals, 2-[3-ethoxy-(4-alkyloxybenzoyloxy)phenyl]benzothiazoles comprising a benzothiazole core, terminal alkoxy chain, ester linker and lateral ethoxy substituent were synthesized and characterized. This series comprises nine members wherein the members differ by the length of alkyloxy chain (CnH2n + 1O-, where n = 2, 4, 6, 8, 10, 12, 14, 16, 18). The thermal properties of the compounds were analyzed by differential scanning calorimetry (DSC), and the textures were identified by polarized optical microscope (POM). The member with the shortest alkoxy chain (n = 2) is a non-mesogen. The remaining members exhibited monotropic nematic phase ranging from the low member (n = 4) until the highest member (n = 18) of the series. The influence of alkoxy chain length on the mesomorphic was studied. In addition, the mesomorphic properties of the benzothiazole liquid crystals were compared with these compounds and the effect of the lateral substituents on their mesomorphism was studied.
