AbstractVarious kinds of polythiophene derivatives were synthesized and thermal properties were examined by DSC, polarized microscopic and X-ray diffraction observations. Fusibility and solubility of these polymers deeply depends upon the polymerization methods and polarity of the mesogenic group. Polymerization was carried out by oxidation and polycondensation methods. The polarity at the end of mesogenic group plays an important role for solubility and fusibility of the polymer in the case of oxidative polymerization. 3-Substituted polythiophene having polar group such as cyano or nitro at the end of mesogenic group was soluble in polar solvent and fusibility at higher temperature. The polymer having polar group at the end of mesogenic group prepared by mild polymerization condition such as polycondensation exhibited a clear smectic texture and also showed electrochemically active by cyclic voltamograms.