Photo-reversible liquid crystal alignment using azobenzene-based self-assembled monolayers : comparison of the bare monolayer and liquid crystal reorientation dynamics

Photosensitive surfaces treated to have in-plane structural anisotropy by illumination with polarized light can be used to orient liquid crystals (LCs). Here we report a detailed study of the dynamic behavior of this process at both short and long times, comparing the ordering induced in the bare ac...

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Publié dans:Langmuir : the ACS journal of surfaces and colloids. - 1985. - 26(2010), 22 vom: 16. Nov., Seite 17482-8
Auteur principal: Fang, Guanjiu (Auteur)
Autres auteurs: Shi, Yue, Maclennan, Joseph E, Clark, Noel A, Farrow, Matthew J, Walba, David M
Format: Article en ligne
Langue:English
Publié: 2010
Accès à la collection:Langmuir : the ACS journal of surfaces and colloids
Sujets:Journal Article
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520 |a Photosensitive surfaces treated to have in-plane structural anisotropy by illumination with polarized light can be used to orient liquid crystals (LCs). Here we report a detailed study of the dynamic behavior of this process at both short and long times, comparing the ordering induced in the bare active surface with that of the LC in contact with the surface using a high-sensitivity polarimeter that enables detailed characterization of the anisotropy of the active surface. The experiments were carried out using self-assembled monolayers (SAMs) made from dimethylaminoazobenzene covalently bonded to a glass surface through a triethoxysilane terminus. This surface gives planar alignment of the liquid crystal director with an azimuthal orientation that can be controlled by the polarization of actinic light. We find a remarkable long-term collective interaction between the orientationally ordered SAM and the director field of the LC: while an azobenzene based SAM in contact with an isotropic gas or liquid relaxes to an azimuthally isotropic state in the absence of light due to thermal fluctuations, an orientationally written SAM in contact with LC in the absence of light can maintain the LC director twist permanently, that is, the SAM is capable of providing azimuthal anchoring to the LC even in the presence of a torque about the surface normal. We find that the short-time, transient LC reorientation is limited by the weak azimuthal anchoring strength of the SAM and by the LC viscosity 
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700 1 |a Shi, Yue  |e verfasserin  |4 aut 
700 1 |a Maclennan, Joseph E  |e verfasserin  |4 aut 
700 1 |a Clark, Noel A  |e verfasserin  |4 aut 
700 1 |a Farrow, Matthew J  |e verfasserin  |4 aut 
700 1 |a Walba, David M  |e verfasserin  |4 aut 
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