V.P. Vorflusev

AZIMUTHAL SURFACE GLIDING OF A NEMATIC LIQUID CRYSTAL

In-plane surface gliding of a thermotropic nematic liquid crystal is investigated at substrates with weak azimuthal anchoring energy under different external electric fields parallel to the substrates. The anchoring is a result of photoinduced anisotropy in a poly-(vinyl)-alcohol alignment layer with embedded azodye molecules. The experimentally measured time constant, which describes the gliding, is inversely proportional to the electric field strength. The surface viscosity value of the liquid crystal director at the substrates extracted from the presented model is estimated as γs⩾0.33 Js/m2.

Azimuthal Anchoring Energy in Photoinduced Anisotropic Films

Most electrooptic effects in liquid crystals require a uniform orientation of the director at the glass substrates. A new method to produce suitable alignment layers is based on the creation of anisotropic polymer films by photopolymerization with linearly polarized light. In the present paper we report on measurements of the anchoring strength of these photo-induced anisotropic films. Using a wedge-cell technique, we find an azimuthal anchoring energy of W≈2.310-6 J/m2.

Bistable Switching in FLC Cells Aligned by Photoanisotropic Films

Abstract Long-term perfect bistable switching of 1,5μm thick Ferroelectric Liquid Crystal (FLC) cell oriented by photoanisotropic (PA) films was demonstrated even in2 case of a large spontaneous polarization Ps=100nC/cm. The condition of a good SmC* orientation quality was shown to be the existence of a nematic phase N*. The bistability properties of PA-films aligned FLC cell, kept for a while in a short-curcuiting state, are easily restored, which is not observed in FLC cells oriented by usual rubbing technique.

Domain structures in ferroelectric liquid crystals

Abstract Domain structures called steric (or striped) domains are investigated in ferroelectric liquid crystals (FLCs). The domain lines are aligned perpendicular to the smectic layers with a period proportional to the FLC cell thickness L. Neither FLC polarization nor helix pitch affects the domain pattern. Striped domains disappear in thick cells (L > 8–10 μm) and transform to a new type of surface domain without any preferred orientation in thin samples (L < 1·0 μm). The existence and structure of the steric domains define properties such as contrast and bistability of the FLC cell. We propose a qualitative explanation of this domain pattern and compare its characteristics with ferroelectric domains discovered earlier by Beresnev et al. in FLCs.

Aligning Properties and Anchoring Strength of Ferroelectric Liquid Crystals

Abstract The review of methods to measure Ferroelectric Liquid Crystal (FLC) anchoring strength are given. The methods are based on measuring the hysteresis and electrooptical dynamic response of FLC. The results of measurements are presented. The ways of future investigations in the field are discussed.

New Type of Monostability and Grey Scale Generation in FLC Cells

Abstract Interaction of surface charges of the FLC spontaneous polarization and mobile ions of a surfac-tant in an alignment layer results in a monostable response of the FLC. Internal field in the FLC bulk induced by the ions of the surfactant in the alignment layer leads to the monostability. Changing the external voltage parameters it is possible to obtain a modulation of a transmitted light (analogue grey scale) in the FLC cells with the alignment layers contained surfactant.

Influence of the Azimuthal Anchoring Energy on the Smectic Layer Formation in Ferroelectric Liquid Crystals

Abstract We have investigated the influence of surface treatment on the memory angle θm in chevron FLC-cells. Surface anisotropy with different azimuthal anchoring energies was produced either by illumination or by rubbing of a PVA layer containing an azo dye. Due to the low pretilt angle (θp <2°), we suppose that the measured value of θm is governed by the tilt angle δ of the smectic layers. A model is presented which relates the equilibrium value of δ to a balance between the azimuthal anchoring energy and the bend energy of the smectic layers in the chevron structure.

Synthesis and physical properties of novel terphenyl type ferroelectric liquid crystals

Abstract A new series of optically active compounds have been prepared using 4,4″-terphenyldicarboxylic acid and S-2-alcoxypropanols-1. These are Sm*C, SmA and N* chemically stable - especially with regard to racemization and UV-light compounds with a small PS value, high twisting power and left handedness of helix.