Synthesis, characterization and mesomorphic properties of new symmetrical dimer liquid crystals derived from benzothiazole

Abstract

Present works report the synthesis and characterization of a series of homologous symmetrical dimers α,ω-bis[4-(6′-methoxybenzothiazol-2′-yl)iminomethylphenoxy]alkane. Total of five members with different lengths of alkyl spacer groups of even parity varying from butyl (C4H8) to dodecyl (C12H24) were prepared and characterized. Infrared and nuclear magnetic resonance (1H and 13C NMR) together with electron-ionization mass spectrometric techniques were employed to confirm the molecular structures of the dimers. The phase phase transition and associated enthalpy changes were obtained using differential scanning calorimetry. Textures studies and mesophase identification were conducted using a polarizing optical microscope attached to hotstage. A diversity of phase-transition behavior was observed as the length of the alkyl spacer increased from C4H8 to C12H24. Almost all title compounds exhibited nematic phase except the dimers containing butyl and hexyl spacers in which the mesomorphic properties were absent.