Article

Preparation of Composites of Polymer Liquid Crystal/Cholesteric Liquid Crystal and Their Photochemical Switching and Memory Properties by Photoisomerization of a Chiral Azobenzene Molecule

Wiley
Journal of Applied Polymer Science
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Abstract

A chiral azobenzene compound was synthesized, and mixing the chiral azobenzene compound in a host nematic liquid crystal (LC) induced a cholesteric phase. The twisting power of the trans-form of the chiral azobenzene compound was larger than that of its cis-form produced by ultraviolet irradiation. A low molecular weight compensated nematic LC was then prepared by mixing of the chiral azobenzene and a nonphotochromic chiral compound, thus giving mutual opposite helical sense in the host LC. Reversible optical switching between transparent and opaque was achieved by ultraviolet and visible light irradiation. However, the photochemically switched opaque state was not stable even in the dark. Stability of the opaque state was found to be improved by adding polymer LC to the low molecular weight compensated nematic LC. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2577–2580, 2004

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... The pitch, the distance over which the director field rotates by 2π radians, is sensitive to external stimuli such as temperature, light, electric field, and mechanical stress [20][21][22][23][24][25]. Kurihara et al. have reported on the photochemical change in transparency as well as the selective reflection of a cholesteric LC (ChLC) resulting from the photoisomerization of a chiral azobenzene compound doped in a host nematic LC [26][27][28][29][30][31]. It is based on the photochemical change in helical twisting power (HTP) of the chiral azobenzene compounds under irradiation of UV and visible light. ...
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