Photoisomerization of azobenzenes and spirocompounds in nematic and in twisted nematic liquid crystals

Samples of a nematic mixture of ZLI1132 and of a twisted nematic mixture composed of ZLI1132 and chiral inductor S811, including 1%-10% (w/w) 4-N,N-dimethylaminoazobenzene (DAB), (4′-nitro)-4-N, Ndimethylaminoazobenzene (NDAB), spiropyran (SP), or spirooxazine (SO) were irradiated to produce the pho...

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Detalles Bibliográficos
Autores principales: Bossi, M.L., Murgida, D.H., Aramendía, P.F.
Formato: JOUR
Materias:
Absorption spectroscopy
Benzene
Birefringence
Isomerization
Monomers
Organic solvents
Photochromism
Raman scattering
Chiral inductor
Mesogenic director
Photochromic transformation
Spirocompounds
Nematic liquid crystals
Acceso en línea:http://hdl.handle.net/20.500.12110/paper_15206106_v110_n28_p13804_Bossi
Aporte de:
Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) de Universidad de Buenos Aires
id todo:paper_15206106_v110_n28_p13804_Bossi
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spelling todo:paper_15206106_v110_n28_p13804_Bossi2023-10-03T16:20:10Z Photoisomerization of azobenzenes and spirocompounds in nematic and in twisted nematic liquid crystals Bossi, M.L. Murgida, D.H. Aramendía, P.F. Absorption spectroscopy Benzene Birefringence Isomerization Monomers Organic solvents Photochromism Raman scattering Chiral inductor Mesogenic director Photochromic transformation Spirocompounds Nematic liquid crystals Samples of a nematic mixture of ZLI1132 and of a twisted nematic mixture composed of ZLI1132 and chiral inductor S811, including 1%-10% (w/w) 4-N,N-dimethylaminoazobenzene (DAB), (4′-nitro)-4-N, Ndimethylaminoazobenzene (NDAB), spiropyran (SP), or spirooxazine (SO) were irradiated to produce the photochromic transformation of the dopant. The changes in the system were monitored by time-resolved transmission spectroscopy, time-resolved birefringence, or polarized Raman scattering. The medium sensitivity of the kinetics and spectroscopy of some of the probes was used to derive information on polarity of the medium. In the systems studied, apart from the changes in absorption spectrum, great changes in birefringence can be photoinduced and the order of the nematic phase can be changed in either direction, depending on the dopant. The open form of SP can discriminate orientation polarity. Although the polarity parallel to the mesogenic director is similar to that for acetone, the perpendicular orientation has a polarity similar to acetonitrile. In agreement with this observation, the kinetics of the Z → E isomerization of NDAB, oriented parallel to the mesogenic director, also experiences a polarity similar to that for acetone. The decay rate constant of the open form of SP displays a linear relationship between its Arrhenius parameters, which is universal in a great variety of homogeneous solvents, solvent mixtures, and liquid crystals, therefore validating the hypothesis that the same type of transformation is observed in all these cases, namely, the decay of the open form monomer. The dopants used have been proven to be adequate probes of bulklike properties in locally heterogeneous systems as liquid crystals. © 2006 American Chemical Society. JOUR info:eu-repo/semantics/openAccess http://creativecommons.org/licenses/by/2.5/ar http://hdl.handle.net/20.500.12110/paper_15206106_v110_n28_p13804_Bossi
institution Universidad de Buenos Aires
institution_str I-28
repository_str R-134
collection Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA)
topic Absorption spectroscopy
Benzene
Birefringence
Isomerization
Monomers
Organic solvents
Photochromism
Raman scattering
Chiral inductor
Mesogenic director
Photochromic transformation
Spirocompounds
Nematic liquid crystals
spellingShingle Absorption spectroscopy
Benzene
Birefringence
Isomerization
Monomers
Organic solvents
Photochromism
Raman scattering
Chiral inductor
Mesogenic director
Photochromic transformation
Spirocompounds
Nematic liquid crystals
Bossi, M.L.
Murgida, D.H.
Aramendía, P.F.
Photoisomerization of azobenzenes and spirocompounds in nematic and in twisted nematic liquid crystals
topic_facet Absorption spectroscopy
Benzene
Birefringence
Isomerization
Monomers
Organic solvents
Photochromism
Raman scattering
Chiral inductor
Mesogenic director
Photochromic transformation
Spirocompounds
Nematic liquid crystals
description Samples of a nematic mixture of ZLI1132 and of a twisted nematic mixture composed of ZLI1132 and chiral inductor S811, including 1%-10% (w/w) 4-N,N-dimethylaminoazobenzene (DAB), (4′-nitro)-4-N, Ndimethylaminoazobenzene (NDAB), spiropyran (SP), or spirooxazine (SO) were irradiated to produce the photochromic transformation of the dopant. The changes in the system were monitored by time-resolved transmission spectroscopy, time-resolved birefringence, or polarized Raman scattering. The medium sensitivity of the kinetics and spectroscopy of some of the probes was used to derive information on polarity of the medium. In the systems studied, apart from the changes in absorption spectrum, great changes in birefringence can be photoinduced and the order of the nematic phase can be changed in either direction, depending on the dopant. The open form of SP can discriminate orientation polarity. Although the polarity parallel to the mesogenic director is similar to that for acetone, the perpendicular orientation has a polarity similar to acetonitrile. In agreement with this observation, the kinetics of the Z → E isomerization of NDAB, oriented parallel to the mesogenic director, also experiences a polarity similar to that for acetone. The decay rate constant of the open form of SP displays a linear relationship between its Arrhenius parameters, which is universal in a great variety of homogeneous solvents, solvent mixtures, and liquid crystals, therefore validating the hypothesis that the same type of transformation is observed in all these cases, namely, the decay of the open form monomer. The dopants used have been proven to be adequate probes of bulklike properties in locally heterogeneous systems as liquid crystals. © 2006 American Chemical Society.
format JOUR
author Bossi, M.L.
Murgida, D.H.
Aramendía, P.F.
author_facet Bossi, M.L.
Murgida, D.H.
Aramendía, P.F.
author_sort Bossi, M.L.
title Photoisomerization of azobenzenes and spirocompounds in nematic and in twisted nematic liquid crystals
title_short Photoisomerization of azobenzenes and spirocompounds in nematic and in twisted nematic liquid crystals
title_full Photoisomerization of azobenzenes and spirocompounds in nematic and in twisted nematic liquid crystals
title_fullStr Photoisomerization of azobenzenes and spirocompounds in nematic and in twisted nematic liquid crystals
title_full_unstemmed Photoisomerization of azobenzenes and spirocompounds in nematic and in twisted nematic liquid crystals
title_sort photoisomerization of azobenzenes and spirocompounds in nematic and in twisted nematic liquid crystals
url http://hdl.handle.net/20.500.12110/paper_15206106_v110_n28_p13804_Bossi
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AT murgidadh photoisomerizationofazobenzenesandspirocompoundsinnematicandintwistednematicliquidcrystals
AT aramendiapf photoisomerizationofazobenzenesandspirocompoundsinnematicandintwistednematicliquidcrystals
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