| Photo-reversible liquid crystal alignment using azobenzene-based self-assembled monolayers: comparison of the bare monolayer and liquid crystal reorientation dynamics. | |
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MedLine Citation:
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PMID: 20929215 Owner: NLM Status: In-Process |
Abstract/OtherAbstract:
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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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Authors:
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Guanjiu Fang; Yue Shi; Joseph E Maclennan; Noel A Clark; Matthew J Farrow; David M Walba |
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Publication Detail:
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Type: Journal Article Date: 2010-10-07 |
Journal Detail:
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Title: Langmuir : the ACS journal of surfaces and colloids Volume: 26 ISSN: 1520-5827 ISO Abbreviation: Langmuir Publication Date: 2010 Nov |
Date Detail:
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Created Date: 2010-11-10 Completed Date: - Revised Date: - |
Medline Journal Info:
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Nlm Unique ID: 9882736 Medline TA: Langmuir Country: United States |
Other Details:
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Languages: eng Pagination: 17482-8 Citation Subset: - |
Affiliation:
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Department of Physics and the Liquid Crystal Materials Research Center, University of Colorado, Boulder, Colorado 80309, United States. |
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From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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