Synthesis of Polythiophene Derivatives Bearing Ferroelectric Liquid Crystalline Substituents

A chiral liquid crystalline (LC) substituent with a fluorine-containing asymmetric moiety was introduced into the 3-position of a thiophene ring. Polymerizations of 2,5-dibrominated thiophene derivatives were carried out through dehalogenative polycondensations. Polythiophene derivatives thus prepared were fusible and soluble in ordinary organic solvents. An absorption band was observed in the range of 400−415 nm. Phase transition behaviors of the polymers and monomers were examined by differential scanning calorimetry, polarizing optical microscopy, and X-ray diffraction analysis. The polymers showed several types of smectic phases in the heating and cooling processes. Additionally, one of the polymers exhibited a striated fan-shaped texture when observed with a polarizing optical microscope. This is attributed to the formation of chiral smectic C (SmC*) phase, which is necessary property to ferroelectricity. Ferroelectric behavior was confirmed by examining the temperature dependence of the dielectric c...