Sequential reaction of monomer synthesis and subsequent electrochemical polymerization in liquid crystal to yield electro-optically active conjugated polymers

Poly(3,4-ethylenedioxythiophene), polythiophene, and poly[1,4-bis(3,4-ethylenedioxythiophene-2-yl)benzene] films with liquid crystal (LC) morphology were synthesized via a sequential two−step polymerization method, combining the Migita−Kosugi−Stille coupling reaction and electrochemical polymerization in a liquid crystal medium. Molecular structures were confirmed using infrared absorption measurements. We conducted surface observations using polarizing optical microscopy, which revealed optical textures corresponding to the liquid crystal (LC) morphology of the polymers formed through molecular assembly imprinting. Cyclic voltammetry measurements were performed to assess the electroactivity of the resultant polymers. Optical properties were evaluated using ultraviolet and visible (UV−vis) and circular dichroism (CD) absorption spectroscopies. The polymers thus obtained in cholesteric LC exhibited electro-chiroptical activities. Electron spin resonance and the CD spectroscopy confirmed the presence of charge carriers in asymmetric environment. The synthesis from monomer to polymer in a liquid crystal can be effectively performed to yield well-formed liquid crystal-imprinted electro-optically active polymers. We achieved a doping driven change in the optical activity of helical conjugated polymers prepared in an asymmetric liquid crystal. In other words, electronic tuning of the optical activity for the polymer atropisomers was achieved.