Chiral Nematic Copolymers with Photoreversible and Irreversible Changing of Helical Supramolecular Structure Pitch

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• 作者：Alexey Yu. Bobrovsky ; Natalia I. Boiko ; and Valery P. Shibaev
• 刊名：Chemistry of Materials
• 出版年：2001
• 出版时间：June 2001
• 年：2001
• 卷：13
• 期：6
• 页码：1998 - 2001
• 全文大小：67K
• 年卷期：v.13,no.6(June 2001)
• ISSN：1520-5002

文摘

A new cholesteric copolymer consisting of nematogenic phenyl benzoate groups and twodifferent types of photosensitive chiral groups, azobenzene- and benzilidene-p-menthan-3-one, was synthesized. Planarly oriented films of copolymer selectively reflect light in thenear-infrared region of spectrum. It was shown that under UV irradiation (365 nm)irreversible untwisting of cholesteric helix takes place and selective light reflection maximumis shifted to the long-wavelength spectral region. This phenomenon is explained by the E-Zisomerization of benzilidene-p-menthan-3-one chiral groups and the decrease of helix twistingpower. On the contrary, under irradiation with visible light (>450 nm), a thermally reversibleshift of selective light reflection peak was observed due to the E-Z isomerization ofazobenzene-containing chiral units. In both cases, cholesteric helix untwisting is explainedby the decrease of the helix twisting power of chiral units during the photoisomerizationprocess. As was demonstrated, such ternary copolymer containing chiral groups sensitiveto the light of different wavelengths may be used for reversible as well as irreversiblerecording of optical information.