T. M. Leslie

Smectic Liquid Crystals

The use of a certain class of liquid crystal materials that exhibit a smectic C phase allows the production of a bistable liquid crystal display element. Such bistable display elements promote the use of matrix addressing for liquid crystal based elements in a display.

Ferroelectric Liquid Crystals - Structure and Design

Abstract Interest in the synthesis of optically active smectic liquid crystals has increased considerably since the advent of a fast switching, bistable, electrooptic device configuration based on their ferroelectric properties. A number of structurally separate ferroelectric liquid crystal phases have been defined which possess differing properties. These types of phase can be utilized in different forms of application. The structures of the various ferroelectric smectic phases and the types of material which exhibit these modifications are discussed in detail. The design and engineering of materials to suit certain device criteria is related to the properties of the smectic ferroelectric phases. A relationship between the absolute spacial configuration of the optically active materials which exhibit ferroelectric smectic phases, the twist direction of the phase and the direction of the spontaneous polarization is developed.

Liquid crystal devices

Liquid crystal devices having excellent speed are produced by utilizing an appropriate liquid crystal mixture. This mixture is prepared by selecting liquid crystal materials having opposite pitch and having specifically chosen spontaneous polarizations.

Liquid-Crystalline Derivatives of S-3,7-dimethyloctan-1-ol

Abstract A wide variety of liquid-crystalline derivatives of S-β-citronellol (S-3,7-dimethyloct-6-ene-1-ol) were prepared and found to exhibit ferroelectric smectic phases. The S-β-citronellol was initially hydrogenated to produce S-3,7-dimethyloctan-1-ol (3M7M8OH). This in turn was either brominated, oxidized, or used in an unchanged form to synthesize a range of materials, many of which exhibited smectic C* phases. The magnitude of the spontaneous polarization for a number of these derivatives was measured. Generally, the materials reported were found to have values for their spontaneous polarizations in the range of 5 to 15 nCcm−2. Many of the materials were also found to have short helical pitches in their C* phases, making them useful as unwinding agents in ferroelectric mixtures.

Some Novel Ferroelectric Smectic Liquid Crystals

Ferroelectric smectic liquid crystals show potential for becoming increasingly important in electrooptic display device applications. However, the numbers of materials available for these applications are limited, particularly those which exhibit ferroelectric, chiral smectic C phases. In this paper we report a number of new systems which exhibit smectic C phases at temperatures close to room temperature making it possible to provide a eutectic mixture which exhibits a stable chiral smectic C phase at room temperature.

Characterization of Two Isomeric Cyano-Ester Homologous Series — I

Current theories concerning the incidence of the reentrant nematic phase in liquid crystals generally incorporate the extent to which the molecules are paired in the nematic phase as a basis for the occurence of reentrant phenomenon. In this study we sought to prepare materials in which the dipolar forces within the constituent molecules could be altered and hence, the degree of pairing in the nematic phase could be changed. Thus, a comparison of the properties of the 4-cyanophenyl 4’-n-alkoxybenzoates with those of the 4-n-alkoxyphenyl 4’-cyanobenzoates was made. It was found that the latter series exhibited unusual properties; an injection of smectic C phases and dual crystalline forms which melted at different temperatures. Indeed, the injection of smectic C properties into the series appears to indicate that the pairing is so strong that the reentrant phase gives way to smectic C formation; this formation in itself is unusual when observed for cyano compounds.

Polarization absorption spectroscopy: Determination of the direction and degree of orientation of absorption transitions

In an ordered, directional medium, such as liquid crystals or biological membranes, it is often desirable to determine both the degree of ordering (i.e., order parameters) and the directions in space which most aptly characterize it. Here, a method is presented for determining these quantities relative to a laboratory frame. It consists in measuring changes in the light absorbed by a pleochroic dye dissolved in dilute quantity in a directionally ordered medium (e.g., nematic liquid crystal or lipid bilayer) as functions of polarization and angles of incidence. The results of testing this method on a model system of dilute mixtures of dyes in a room temperature nematic liquid crystal are presented. In principle, only six such measurements are necessary to make these determinations; however, some redundancy is desirable to obtain sufficiently accurate results. We show that an accuracy of 5% or better can be obtained from nine measurements. A detailed discussion of the errors that can be expected is given.

The Synthesis and Characterization of Some Perylene and Anthraquinoic Dichroic Dyes for Liquid Crystal Display Applications

A series of dyes utilizing perylene as a fluorescent dichroic chomophore have been synthesized and their order parameters measured. For the N,N’-di-n-alkylperylene -3,4,9,10 — diimides, order parameters in the commercially available liquid crystal mixture E7, ranging from 0.723 to 0.745 (corresponding to dichroic ratios of 8.7 to 13.8) were obtained. The dichroic ratio was obtained by measuring the polarized absorption spectra in both the parallel and perpendicular directions to the nematic director and dividing the parallel component by the perpendicular one (A∥/A⊥). Further non- fluorescent derivatives of perylene tetracarboxylic-3,4,9,10- dianhydride have been synthesized and their properties characterized. Alternative dyes employing the 2,6-diaminoanthraquinone chromophore have been synthesized and their order parameters also measured. Order parameters in E7 ranging from 0.66 to 0.69 (dichroic ratio 5.5 to 5.8) have been obtained for diazo and diazoxybenzene derivatives of this chromophore under the same conditions.