Soft matter, possessing both flexibility and robustness, is widely used in various fields from biological systems to electrical appliances. Soft matter includes polymers, colloids, gels, liquid crystals and biological tissues, among which, we have investigated physical properties of liquid crystals (LCs) and their composites. LC is known as the fourth state of matter that occurs between solid and liquid, and is characterized by the liquid-like fluidity and the structural and optical anisotropies as a crystal. Thanks to the dual nature, LCs are used not only for flat panel displays but also for many other applications such as optical films, retarders, thermometers and cosmetics.

Among various phases of LCs, one of our interests is smectic (Sm) phases that have the layered structure composed of the rod-like molecules. Figure 1 shows the schematic figure of SmA (two-dimensional liquid) phase and SmE phase. Recently, SmE phase, regarded as a soft crystal with the long-ranged positional order in the layer plane, has been spotlighted as a semiconductor, since it showed such high carrier mobility as
10 cm²/Vs. Another advantage of SmE phase is the ability of forming thin films with uniform thickness and homogeneous molecular alignment, due to the liquid crystalline self-organization. Thanks to these excellent properties, SmE phase is a promising candidate for new electric devices, but there is one problem that not many compounds take stable SmE phase in a wide temperature range.

Recently, we found that binary mixtures of simple LC compounds can form SmE phase when mixed at 1:1 molar ratio. When one of the two compounds is an electron acceptor and the other works as a donor, they exhibit highly ordered smectic phases, called induced phases, due to the intermolecular charge-transfer. Unlike the single-component SmE phase, the two compounds arranged alternatively in the herringbone lattice in the induced SmE phase, the lower symmetry of which gives rise to different electrical and optical anisotropies from the usual SmE phase. Furthermore, under an external field perpendicular to the layer plane, the induced SmE films loses the mirror symmetry as well as the up-down symmetry, which causes the rotary function. We have studied the mechanical and electric properties of the induced SmE phase, expecting that it can be used for novel electric devices.