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Liquid Crystals - Thermally and Electrically Induced Textural Changes in Cholesteric Phases


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Formation of focal-conic structure with superimposed fingerprint texture. Continuous increase in temperature leads to an increase in the distance between the dark and bright strips.Nematic Phase. Field of view partially dark due to homogeneous orientation.Reappearance of fingerprint pattern above nematic
temperature.Continuous reduction in distance between dark strips. Transition to isotropic
phase leading to completely dark field of view. Cooling from the isotropic phase leads again to focal-conic texture. The fingerprint texture is formed again. Slow transformation to the nematic phase.Below the nematic temperature the focal-conic structure is formed again. Transition
from isotropic to cholesteric state upon cooling. Bright patches are
formed which are confined by dark edges. Formation of fingerprint textures. Simultaneously, Maltese cross-like structures are embedded in this texture. The nematic phase ensues. It remains homogeneously orientated over a fairly large temperature range. Below the nematic temperature, the cholesteric phase is again resumed.Fingerprint texture with characteristic spacing between strips
in the absence of an
electric field. Increasing constant electric
field. The distance between the dark strips increases continuously. Unwinding of helical twist. Transition to a homogeneously orientated nematic phase. Completely dark field of view at maximum field strength. Decreasing voltage. Formation of cholesteric nuclei. The cholesteric phase develops from these nuclei. Continuous decrease in the spacing of the dark strips.
Cholesteric phase with large pitch. Increasing distance between dark strips, with increasing field strength. Homeotropic orientation over large variation in electric field strength, due to orientating effect of lecithin. Reformation of cholesteric phase with decreasing voltage. A renewed short increase in voltage. Decreasing field strength again.
Computer animation
Computer animation


Formal Metadata

Title Liquid Crystals - Thermally and Electrically Induced Textural Changes in Cholesteric Phases
Alternative Title Flüssige Kristalle - Thermisch und elektrisch induzierte Texturänderungen bei cholesterischen Phasen
Author Sackmann, Erich
License CC Attribution - NonCommercial - NoDerivatives 3.0 Germany:
You are free to use, copy, distribute and transmit the work or content in unchanged form for any legal and non-commercial purpose as long as the work is attributed to the author in the manner specified by the author or licensor.
DOI 10.3203/IWF/E-2140eng
IWF Signature E 2140
Publisher IWF (Göttingen)
Release Date 1977
Language English
Producer IWF
Production Year 1974

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IWF Technical Data Film, 16 mm, LT, 79 m ; F, 7 1/2 min

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Subject Area Chemistry
Abstract Microscopic shots in mixtures of cholesterinechloride and cholesterine-laurate. Cholesteric phases with characteristic patterns ("Fingerprint"-structure), that develop into typical nematic thread structure.
Keywords crystals / liquid crystals
cholesteric phase
fingerprint texture
liquid crystals
nematic texture

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