In this paper we present selected members of 7 new series of bent-shaped five-ring resorcinol derivatives which are distinguished by substituents at the central core as well as at the outer rings. Depending on the kind and position of the substituents and depending on the length of the terminal chains not only have new mesophases (the C PA phase or three unidentified B 2 -like phases) been identified, but also interesting phase sequences have been observed (B 2 -N; B 2 -SmA; B 2 -SmA-SmC; B 2 -SmA-SmC-N).

We report unambiguous experimental evidence for an achiral orthogonal biaxial smectic-A phase which exhibits antiferroelectric switching behavior. The evidence is based on x-ray-diffraction measurements, texture observation, and the results of dielectric and electro-optical measurements.

No abstract

A small amount of azo-dendrimer molecules dissolved in a liquid crystal enables translational and rotational motions of microrods in a liquid crystal matrix under unpolarized UV light irradiation. This motion is initiated by a light-induced trans-to-cis conformational change of the dendrimer adsorbed at the rod surface and the associated director reorientation. The bending direction of the cis conformers is not random but is selectively chosen due to the curved local director field in the vicinity of the dendrimer-coated surface. Different types of director distortions occur around the rods, depending on their orientations with respect to the nematic director field. This leads to different types of motions driven by the torques exerted on the particles by the director reorientations.L iquid crystals (LCs) are self-organized mesomorphic materials that exhibit various symmetries and structures (1). They are widely used in flat panel displays for their exceptional electrooptical properties and a combination of orientational elasticity and fluidity. For example, nematic LCs (NLCs) are distinguished by their long-range orientational order, which favors alignment of the molecules (mesogens) in a preferred direction denoted as the director n. An exceptional feature of NLCs is that, despite their fluidity, they exhibit anisotropic optical and mechanical properties, and thus can transmit mechanical torque because of directional elasticity (1). Such torque occurs in response to deformations away from a uniform equilibrium state.Such unique features of LCs can be exploited for designing smart multifunctional materials. Among these materials, colloidal dispersions of microparticles and nanoparticles in LCs have been actively studied in research on soft-matter physics (2-7). Tunable anisotropic interactions between microparticles dispersed in LCs give rise to self-assembled 1D and 2D colloidal structures (6,8,9). Such colloidal dispersions are interesting not only from a fundamental point of view but also from a technological one. A wide range of self-assembled structures of particles and topological defects stabilized by LC-mediated interactions find numerous applications in designing metamaterials (10), photonic devices (5, 11), sensors (12), and microrheology (5,(10)(11)(12). Here, we demonstrate a phenomenon that can be used in intelligent devices using colloidal dispersions: controlled light-driven translational and rotational motions of microrods in a NLC matrix.The orientation of LC molecules at an interface is governed by anchoring conditions, i.e., whether the director is perpendicular (homeotropic) or parallel (planar) to the interface. The orientation of the director at surfaces can be controlled through interfacial energy, anisotropy of the surface tension, and surface topography, by the pretreatment of the surfaces using surface agents, such as polymers and surfactants, together with mechanical or optical treatments. In most of the previous experiments, the solid interface was fixed. Here we use a so-called comm...

Ferroelectric liquid crystalline phases formed by achiral bent-core mesogens have been known for about seven years. However, only few materials have been found to exhibit both conventional nematic/smectic mesophases and '' banana '' phases, where steric packing of bent mesogens results in ferroelectric properties.In this paper we report some studies of such compounds showing transitions between paraelectric smectic A, smectic C and antiferroelectric smectic CP phases. Structure characterization as well as studies of ordering in mesophases have been performed with the help of a variety of experimental techniques including X-ray diffraction, NMR and dielectric spectroscopy as well as electrooptical measurements.