An anomalously large dielectric permittivity of ≈10 is found in the mesophase temperature range (MP phase) wherein high fluidity is observed for a liquid-crystal compound having a 1,3-dioxane unit in the mesogenic core (DIO). In this temperature range, no sharp X-ray diffraction peak is observed at both small and wide Bragg angles, similar to that for a nematic phase; however, an inhomogeneous sandy texture or broken Schlieren one is observed via polarizing optical microscopy, unlike that for a conventional nematic phase. DIO exhibits polarization switching with a large polarization value, i.e., P = 4.4 µC cm , and a parallelogram-shaped polarization-electric field hysteresis loop in the MP phase. The inhomogeneously aligned DIO in the absence of an electric field adopts a uniform orientation along an applied electric field when field-induced polarization switching occurs. Furthermore, sufficiently larger second-harmonic generation is observed for DIO in the MP phase. Second-harmonic-generation interferometry clearly shows that the sense of polarization is inverted when the +/- sign of the applied electric field in MP is reversed. These results suggest that a unidirectional, ferroelectric-like parallel polar arrangement of the molecules is generated along the director in the MP phase.

We report a polymer-stabilized blue phase liquid crystal (BPLC) whose Kerr constant is about 2.2× larger than previous record. When filled in a 3.2-μm-thick vertical field switching cell, the on-state voltage is merely 8.4 V (at λ = 514 nm) while keeping submillisecond response time and negligible hysteresis (<1%) at the room temperature. These results imply that the dawn of BPLC era for high speed display and photonic devices has finally arrived.

Organic materials whose refractive indexes can be controlled by applying an electric field have great potential in the field of electro-optics due to their processability, possibility of fabrication over large areas, and compatibility with mechanically flexible substrates. From the viewpoint of practical applications, the device thickness and the applied voltage should both be small. This requires materials with large electro-optic coefficients.The Kerr effect is a kind of quadratic electro-optic effect, which is mainly caused by the electric-field-induced orientation of polar molecules in optically transparent and isotropic materials.[1±3] The Kerr effect follows Equation 1, [4] Dn(E) = kKE 2where Dn(E) is the induced birefringence, K is the Kerr constant, E is the applied electric field, and k is the probe wavelength. An anomalously large Kerr effect is observed in nematic liquid crystals in an isotropic phase just above the nematic±isotropic phase-transition temperature. This is because the isotropic phase has nematic-like short-range ordering on a length scale defined by a coherence length, n. The Kerr constant of nematic liquid crystals in an isotropic phase diverges as the temperature decreases to T*, which is the critical temperature where n grows infinitely, and is typically 1 K smaller than the nematic±isotropic transition temperature, T NI . The strong temperature dependence of large Kerr constants and the narrow temperature range in which it is seen makes the practical use of this phenomenon difficult. The temperature dependence of K and n can be expressed by Equation 2 based on the Landau±de Gennes theory.[5]A key challenge in electro-optics from the applications viewpoint is to expand the temperature range in which the anomalously large Kerr effect occurs, and to make it relatively insensitive to temperature. If the size of nematic order is limited, that is, if the growth of n is suppressed to a finite size that is less than the wavelength of visible light, below T NI an anomalously large Kerr effect is expected to appear over a broad temperature range below T NI , with low temperature dependence. Our approach has been to build partitions in the liquid crystal so as to divide the long-range-ordered regions of the liquid crystal into smaller domains comparable to n in an isotropic phase just above T NI . It is known that a microemulsion based on a liquid crystal can induce an isotropic state below T NI .[6] Also, it is known that polymers formed in liquid crystals can serve to disperse the liquid-crystal domains into small isolated droplets (so-called polymer-dispersed liquid crystals (PDLCs)), [7±9] to stabilize a certain orientation [10,11] or to expand the temperature range of a blue phase. [12,13] Therefore, polymer networks with an appropriate mesh size are expected to suppress the growth of n in a liquid crystal. In this paper, we present a novel induced isotropic phase with a large electro-optic Kerr effect, created by photopolymerizing a small amount of the monomers in chiral liquid crystals....

The relationship between material parameters of host nematic liquid crystals (LCs) and Kerr constant of their nanostructured chiral LC composites was investigated. We made certain that the Kerr constant of nanostrutured chiral LC composites was closely related to the parameters of their host LCs, such as value of the difference of refractive index (Δn), the dielectric anisotropy (Δε), and bend to splay elastic constant ratio (K33∕K11).