We studied the electro-optical response of a bistable cholesteric texture (BCT) display to ac voltage pulses. The material can be driven into states where planar and focal conic textures coexist at zero field and gray scale memory is achieved. According to the properties of the BCT display we designed two drive schemes; one for binary operation and the other for gray scale operation. We made a 320×320 pixel reflective display with a resolution of 80 lines/in. on a passive matrix. Measurement in an integration chamber showed that the display has higher contrast and better viewing angle than a reflective super twisted nematic display.
Deuterium NMR spectra from a set of cholesteric materials differing in pitch length have been interpreted in terms of a biaxial ordering of the molecules. It is found that, in these materials, the biaxiality in the cholesteric phase is a universal function of the reduced temperature (independent of pitch length) only when there is a blue phase present in the material. In contrast, when the cholesteric phase transforms directly into the isotropic phase without the presence of a blue phase the biaxiality on a reduced-temperature plot is strongly pitch-length dependent. By the study of different deuterated sites of the same molecule, the mechanism for biaxiality is examined. Deuterium NMR spectra are also used to measure the pitch dependence of the self-diffusion constant. Finally, the NMR technique of measuring biaxiality in the cholesteric phase is discussed and a critique made. The materials used in the study were selectively deuterated 4-methoxybenzylidene-4'butylaniline (MBBA) twisted by the addition of chiral 4-methoxybenzylidene-4 -[( + )-2methylbutyl]aniline (MBMBA) in various weight percentages to obtain samples of different pitch lengths.
This paper reports observation, in a mixture of potassium palmitate-rfg, potassium laurate, and water, of a lamellar phase above 41 °C, a phase of elongated cylindrical aggregates below 36°C, and, in the intermediate temperature region, a phase in which the ^H-NMR spectral patterns can be calculated from a model of elongated ribbon-shaped aggregates. The size of the ribbons can be determined from the spectra and is found to vary with temperature. The results are consistent with ^H-NMR spectra of ^HgO in the same and other ternary mixtures.
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