Sign inversion of spontaneous polarization in ferroelectric liquid crystal mixtures

Sign inversion of spontaneous polarization (Ps) has been studied in two types of mixture systems of ferroelectric liquid crystal (FLC). One is a binary mixture of chiral (ferroelectric) and achiral SmC liquid crystals. Although the pure FLC has a relatively large Ps and shows no anomaly in the sign of Ps, the magnitude of Ps exponentially decreases upon doping with achiral compound. Particularly, in the mixture highly doped with achiral compound, which shows extremely small Ps, the sign of Ps is inverted upon changing temperature. In this case, the inversion temperature is very sensitive to the concentration of achiral dopant. Another system is a mixture of two FLCs having opposite signs of Ps. In this mixture, the sign inversion has been observed with temperature in the concentration range in which Ps is suppressed.