Determination of the Cholesteric Screw Sense

Heppke, G.; Oestreicher, F.

doi:10.1080/00268947808070309

Cited by 76 publications

(38 citation statements)

References 11 publications

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“…The nonspectroscopic methods are usually based on the observation of the cholesteric phase with an optical microscope in linearly polarized light. Some of these are modification of the Grandjean-Cano method [14][15][16][17] based on the observation of the disclination lines that appear when a cholesteric is inserted in a variable-pathlength cell whose windows are appropriately rubbed to obtain the necessary alignment. The lens version is illustrated in Figure 2.…”

Section: The Cholesteric Inductionmentioning

confidence: 99%

Chiral doping of nematic phases and its application to the determination of absolute configuration

2007

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Doping nematic liquid crystals with nonracemic chiral compounds induces a twisted nematic (cholesteric) phase. The ability of solutes to twist the nematic phase may be related to the overall shape of the chiral dopant and consequently to its absolute configuration. The cholesteric induction is therefore a powerful tool complementary to chiroptical techniques to obtain stereochemical information on chiral molecules.

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Section: The Cholesteric Inductionmentioning

confidence: 99%

Chiral doping of nematic phases and its application to the determination of absolute configuration

2007

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“…Cholesteric pitches were determined with the Grandjean-Cano technique (33). For this purpose, the aligned sample was prepared as described above and covered with a plane-convex lens of known radius (Linos Components; Radiometer, The Netherlands).…”

Section: Measurement Of Cholesteric Pitches and Reflection Wavelengthsmentioning

confidence: 99%

Unidirectional rotary motion in a liquid crystalline environment: Color tuning by a molecular motor

Delden

Koumura

Harada³

et al. 2002

Proc. Natl. Acad. Sci. U.S.A.

183

105

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Life could not exist without motion induced by a variety of molecular motors. The construction of artificial motors by chemical synthesis, which can power motions that lead to macroscopic detectable effects in a system, is a major endeavor in contemporary science. To move toward this goal, a host-guest system, composed of a nematic liquid crystal film doped with a chiral light-driven molecular motor, is assembled. Irradiation of the film results in unidirectional rotary motion of the molecular motor, which induces a motion of the mesogenic molecules leading to a molecular reorganization and, as a consequence, a change in the color of the film. In this way, by control of the rotary motion at the molecular level, color tuning over the entire visible spectrum is achieved. These findings demonstrate that a molecular motor can exert a visually observable macroscopic change in a material.

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“…31 It should be stressed that this is not a spectroscopic method and gives results completely independent from those obtained with CD or optical rotation. Another technique widely used to measure the cholesteric pitch is based on the Bragg scattering of monochromatic light (obtained by a helium-neon laser) from fingerprint or planar textures of the cholesteric 32 : Its angular dependence is strictly related to the cholesteric pitch.…”

Section: Methodsmentioning

confidence: 97%

“…29 This method is used mainly with thermotropic cholesterics with long pitch. In the most practical arrangement, 30,31 a plano-convex lens and a flat piece of glass are used, both treated (by coating and/or rubbing) to orient molecules in a planar way, parallel to the same direction. The cholesteric sample is introduced between the two surfaces; the cholesteric helices have their axes perpendicular to the surfaces, and a series of concentric circular disclinations can be seen with a microscope (Figure 7.7).…”

Section: Methodsmentioning

confidence: 99%