Ferroelectric liquid crystal cell versus dye doped ferroelectric liquid crystal cells: A comparison of dielectric properties

We report the dielectric dispersion and ferroelectric response of a ferroelectric liquid crystal (FLC) mixture after doping with anthraquinone dye at two different concentrations (0.5% and 2.5% w/w). Dielectric and polarization switching properties of the FLC mixture and that of the dye-doped FLC mixtures are investigated as a function of temperature. It is observed that the dielectric data in the low concentration dye-doped mixture are comparable to that of the undoped FLC compound. On the other hand the real part of dielectric permittivity is significantly reduced when the concentration of the dye is increased to 2.5%. Temperature dependence of spontaneous polarization and response time is measured and that supports the dielectric results. We also evaluated the rotational viscosity and activation energy. The SmC*-SmA* transition temperature is decreased by the addition of dye and that shift with temperature is discussed with the help of the Landau theory.