High-sensitivity aminoazobenzene chemisorbed monolayers for photoalignment of liquid crystals

We describe a new type of optically controlled liquid crystal alignment layer that demonstrates unprecedented performance. It consists of an aminoazobenzene-type material with a very simple molecular structure, which is derived from methyl red by a one-step synthesis. We have devised a method of for...

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Veröffentlicht in:Langmuir : the ACS journal of surfaces and colloids. - 1985. - 25(2009), 2 vom: 20. Jan., Seite 997-1003
1. Verfasser: Yi, Youngwoo (VerfasserIn)
Weitere Verfasser: Farrow, Matthew J, Korblova, Eva, Walba, David M, Furtak, Thomas E
Format: Online-Aufsatz
Sprache:English
Veröffentlicht: 2009
Zugriff auf das übergeordnete Werk:Langmuir : the ACS journal of surfaces and colloids
Schlagworte:Journal Article Research Support, U.S. Gov't, Non-P.H.S. Membranes, Artificial p-Aminoazobenzene 57X2AH42T1
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520 |a We describe a new type of optically controlled liquid crystal alignment layer that demonstrates unprecedented performance. It consists of an aminoazobenzene-type material with a very simple molecular structure, which is derived from methyl red by a one-step synthesis. We have devised a method of forming covalently attached monolayers of this material on glass by an amine-assisted condensation reaction involving the triethoxysilane end of the molecule. A nematic liquid crystal (LC) cell made with the monolayer and a rubbed polymer layer was switched from a uniform state to a twisted state with a polarized 450 nm control beam having a dose of 5.5 mJ/cm(2). This is equivalent to an average of only one absorbed photon per azobenzene group. Through atomic force microscopy, absorption spectroscopy, spectroscopic ellipsometry, and second harmonic generation experiments, we have confirmed that layers of this type are smooth and uniform with a surface coverage consistent with a monolayer and that the azobenzene groups are tilted, on average, 55 degrees with respect to the surface normal. These characteristics lead to a large interaction energy density between the layer and LC. The monolayer's rapid response in developing anisotropy in this property can be attributed to a large absorption cross section, as well as the favorable tilt angle, which allows for sufficient photoisomerization free volume in a dense layer 
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700 1 |a Farrow, Matthew J  |e verfasserin  |4 aut 
700 1 |a Korblova, Eva  |e verfasserin  |4 aut 
700 1 |a Walba, David M  |e verfasserin  |4 aut 
700 1 |a Furtak, Thomas E  |e verfasserin  |4 aut 
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