Reversible Isothermal Twist-Bend Nematic-Nematic Phase Transition Driven by the Photoisomerization of an Azobenzene-Based Nonsymmetric Liquid Crystal Dimer

Daniel A Paterson, Jie Xiang, Gautam Singh, Rebecca Walker, Deña M Agra-Kooijman, Alfonso Martinez-Felipe, Min Gao, John M D Storey, Satyendra Kumar, Oleg D Lavrentovich, Corrie T Imrie

Research output: Contribution to journalArticle

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Abstract

The liquid crystal nonsymmetric dimer, 1-(4-butoxyazobenzene-4'-yloxy)-6-(4-cyanobiphenyl-4'-yl) hexane (CB6OABOBu), shows enantiotropic twist-bend nematic, NTB, and nematic, N, phases. The NTB phase has been confirmed using polarized light microscopy, freeze fracture transmission electron microscopy, and X-ray diffraction. The helicoidal pitch in the NTB phase is 18 nm. The NTB-N (TNTBN) and N-I (TNI) transition temperatures are reduced upon UV light irradiation, with the reduction in TNTBN being much larger than that in TNI. An isothermal, reversible NTB-N transition may be driven photochemically. These observations are attributed to a trans-cis photoisomerization of the azobenzene fragment on UV irradiation, with the cis isomers stabilizing the standard nematic phase and the trans isomers stabilizing the NTB phase. The dramatic changes in TNTBN provide evidence that the transition between the normal nematic and twist-bend nematic with spontaneous breaking of chiral symmetry is crucially dependent on the shape of molecular dimers, which changes greatly during the trans-cis isomerization.

Original languageEnglish
Pages (from-to)5283-5289
Number of pages7
JournalJournal of the American Chemical Society
Volume138
Issue number16
Early online date25 Mar 2016
DOIs
Publication statusPublished - 27 Apr 2016

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Polarization Microscopy
Photoisomerization
Liquid Crystals
Azobenzene
Transition Temperature
Phase Transition
Hexanes
Ultraviolet Rays
Transmission Electron Microscopy
X-Ray Diffraction
Isomers
Dimers
Liquid crystals
Phase transitions
Irradiation
Light polarization
Isomerization
Hexane
Ultraviolet radiation
Superconducting transition temperature

Cite this

Reversible Isothermal Twist-Bend Nematic-Nematic Phase Transition Driven by the Photoisomerization of an Azobenzene-Based Nonsymmetric Liquid Crystal Dimer. / Paterson, Daniel A; Xiang, Jie; Singh, Gautam; Walker, Rebecca; Agra-Kooijman, Deña M; Martinez-Felipe, Alfonso; Gao, Min; Storey, John M D; Kumar, Satyendra; Lavrentovich, Oleg D; Imrie, Corrie T.

In: Journal of the American Chemical Society, Vol. 138, No. 16, 27.04.2016, p. 5283-5289.

Research output: Contribution to journalArticle

Paterson, Daniel A ; Xiang, Jie ; Singh, Gautam ; Walker, Rebecca ; Agra-Kooijman, Deña M ; Martinez-Felipe, Alfonso ; Gao, Min ; Storey, John M D ; Kumar, Satyendra ; Lavrentovich, Oleg D ; Imrie, Corrie T. / Reversible Isothermal Twist-Bend Nematic-Nematic Phase Transition Driven by the Photoisomerization of an Azobenzene-Based Nonsymmetric Liquid Crystal Dimer. In: Journal of the American Chemical Society. 2016 ; Vol. 138, No. 16. pp. 5283-5289.
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title = "Reversible Isothermal Twist-Bend Nematic-Nematic Phase Transition Driven by the Photoisomerization of an Azobenzene-Based Nonsymmetric Liquid Crystal Dimer",
abstract = "The liquid crystal nonsymmetric dimer, 1-(4-butoxyazobenzene-4'-yloxy)-6-(4-cyanobiphenyl-4'-yl) hexane (CB6OABOBu), shows enantiotropic twist-bend nematic, NTB, and nematic, N, phases. The NTB phase has been confirmed using polarized light microscopy, freeze fracture transmission electron microscopy, and X-ray diffraction. The helicoidal pitch in the NTB phase is 18 nm. The NTB-N (TNTBN) and N-I (TNI) transition temperatures are reduced upon UV light irradiation, with the reduction in TNTBN being much larger than that in TNI. An isothermal, reversible NTB-N transition may be driven photochemically. These observations are attributed to a trans-cis photoisomerization of the azobenzene fragment on UV irradiation, with the cis isomers stabilizing the standard nematic phase and the trans isomers stabilizing the NTB phase. The dramatic changes in TNTBN provide evidence that the transition between the normal nematic and twist-bend nematic with spontaneous breaking of chiral symmetry is crucially dependent on the shape of molecular dimers, which changes greatly during the trans-cis isomerization.",
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note = "D.A.P. would like to thank the RSC’s mobility grant award scheme for funding of a research trip to the Liquid Crystal Institute at Kent State University. R.W. gratefully acknowledges the Carnegie Trust for the Universities of Scotland for the award of a vacation scholarship. G.S., D.M.A.-K., and S.K. gratefully acknowledge support for x-ray work from the Division of Basic Energy Sciences, Office of Science of the US Department of Energy under award DE-SC-0001412. ODL acknowledges support from NSF DMR-1410378 grant. The TEM data were obtained at the TEM facility at the Liquid Crystal Institute, Kent State University, supported by the Ohio Research Scholars Program “Research Cluster on Surfaces in Advanced Materials”",
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AU - Singh, Gautam

AU - Walker, Rebecca

AU - Agra-Kooijman, Deña M

AU - Martinez-Felipe, Alfonso

AU - Gao, Min

AU - Storey, John M D

AU - Kumar, Satyendra

AU - Lavrentovich, Oleg D

AU - Imrie, Corrie T

N1 - D.A.P. would like to thank the RSC’s mobility grant award scheme for funding of a research trip to the Liquid Crystal Institute at Kent State University. R.W. gratefully acknowledges the Carnegie Trust for the Universities of Scotland for the award of a vacation scholarship. G.S., D.M.A.-K., and S.K. gratefully acknowledge support for x-ray work from the Division of Basic Energy Sciences, Office of Science of the US Department of Energy under award DE-SC-0001412. ODL acknowledges support from NSF DMR-1410378 grant. The TEM data were obtained at the TEM facility at the Liquid Crystal Institute, Kent State University, supported by the Ohio Research Scholars Program “Research Cluster on Surfaces in Advanced Materials”

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N2 - The liquid crystal nonsymmetric dimer, 1-(4-butoxyazobenzene-4'-yloxy)-6-(4-cyanobiphenyl-4'-yl) hexane (CB6OABOBu), shows enantiotropic twist-bend nematic, NTB, and nematic, N, phases. The NTB phase has been confirmed using polarized light microscopy, freeze fracture transmission electron microscopy, and X-ray diffraction. The helicoidal pitch in the NTB phase is 18 nm. The NTB-N (TNTBN) and N-I (TNI) transition temperatures are reduced upon UV light irradiation, with the reduction in TNTBN being much larger than that in TNI. An isothermal, reversible NTB-N transition may be driven photochemically. These observations are attributed to a trans-cis photoisomerization of the azobenzene fragment on UV irradiation, with the cis isomers stabilizing the standard nematic phase and the trans isomers stabilizing the NTB phase. The dramatic changes in TNTBN provide evidence that the transition between the normal nematic and twist-bend nematic with spontaneous breaking of chiral symmetry is crucially dependent on the shape of molecular dimers, which changes greatly during the trans-cis isomerization.

AB - The liquid crystal nonsymmetric dimer, 1-(4-butoxyazobenzene-4'-yloxy)-6-(4-cyanobiphenyl-4'-yl) hexane (CB6OABOBu), shows enantiotropic twist-bend nematic, NTB, and nematic, N, phases. The NTB phase has been confirmed using polarized light microscopy, freeze fracture transmission electron microscopy, and X-ray diffraction. The helicoidal pitch in the NTB phase is 18 nm. The NTB-N (TNTBN) and N-I (TNI) transition temperatures are reduced upon UV light irradiation, with the reduction in TNTBN being much larger than that in TNI. An isothermal, reversible NTB-N transition may be driven photochemically. These observations are attributed to a trans-cis photoisomerization of the azobenzene fragment on UV irradiation, with the cis isomers stabilizing the standard nematic phase and the trans isomers stabilizing the NTB phase. The dramatic changes in TNTBN provide evidence that the transition between the normal nematic and twist-bend nematic with spontaneous breaking of chiral symmetry is crucially dependent on the shape of molecular dimers, which changes greatly during the trans-cis isomerization.

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