Ефекти УФ-випромінювання на спіральне закручування у холестеричних системах, що містять фоточутливі азокси-нематики
For cholesteric liquid crystal systems containing photosensitive nematic ZhK-440 and a mixture of cholesterol derivatives, the changes in helical twisting induced by UV radiation are studied. The UV-induced shift of the selective reflection maximum λmax is shown to depend on the concentration of the...
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| Date: | 2012 |
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| Main Authors: | , , |
| Format: | Article |
| Language: | English |
| Published: |
Publishing house "Academperiodika"
2012
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| Subjects: | |
| Online Access: | https://ujp.bitp.kiev.ua/index.php/ujp/article/view/2021349 |
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| Journal Title: | Ukrainian Journal of Physics |
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Ukrainian Journal of Physics| Summary: | For cholesteric liquid crystal systems containing photosensitive nematic ZhK-440 and a mixture of cholesterol derivatives, the changes in helical twisting induced by UV radiation are studied. The UV-induced shift of the selective reflection maximum λmax is shown to depend on the concentration of the nematic component. For low concentrations of ZhK-440, λmax increases, which correlates with the corresponding temperature-induced changes. For higher azoxy nematic concentrations, λmax decreases, regardless of the temperature behavior of the system. To explain the experimental data, a theoretical description is proposed on the basis of the development of molecular models of helical twisting. Good agreement was obtained between calculated and measured values of the UV-induced shift as a function of the azoxy nematic concentration, with two extrema and an inversion point. The extra twisting arises from the cholesteric mesophase-induced orientation of short molecular axes of cis-isomers formed as a result of irradiation. |
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