| Surface shear rheology of saponin adsorption layers. | |
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MedLine Citation:
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PMID: 22830458 Owner: NLM Status: Publisher |
Abstract/OtherAbstract:
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Saponins are a wide class of natural surfactants, with molecules containing a rigid hydrophobic group (triterpenoid or steroid), connected via glycoside bonds to hydrophilic oligosaccharide chains. These surfactants are very good foam stabilziers and emulsifiers, and show a range of non-trivial biological activities. The molecular mechanisms behind these unusual properties are unknown and, therefore, the saponins have attracted significant research interest in the recent years. In our previous study (Stanimirova et al., Langmuir 2011) we showed that the triterpenoid saponins extracted from Quillaja saponaria plant (Quillaja saponins) formed adsorption layers with unusually high surface dilatational elasticity, 280 ± 30 mN/m. In the current paper we study the shear rheological properties of the adsorption layers of Quillaja saponins. In addition, we study the surface shear rheological properties of Yucca saponins which are of steroid type. The experimental results show that the adsorption layers of Yucca saponins exhibits purely viscous rheological response, even at the lowest shear stress applied, whereas the adsorption layers of Quillaja saponins behave like a viscoelastic two-dimensional body. For Quillaja saponins, single master curve describes the data for the viscoelastic creep compliance vs. deformation time, up to a certain critical value of the applied shear stress. Above this value, the layer compliance increases and the adsorption layers eventually transform into viscous ones. The experimental creep-relaxation curves for the viscoelastic layers are fitted very well by compound Voigt rheological model. The obtained results are discussed from the viewpoint of the layer structure and the possible molecular mechanisms, governing the rheological response of the saponin adsorption layers. |
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Authors:
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Konstantin Golemanov; Slavka Tcholakova; Nikolai Denkov Denkov; Eddie G Pelan; Simeon D Stoyanov |
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Publication Detail:
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Type: JOURNAL ARTICLE Date: 2012-7-25 |
Journal Detail:
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Title: Langmuir : the ACS journal of surfaces and colloids Volume: - ISSN: 1520-5827 ISO Abbreviation: - Publication Date: 2012 Jul |
Date Detail:
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Created Date: 2012-7-26 Completed Date: - Revised Date: - |
Medline Journal Info:
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Nlm Unique ID: 9882736 Medline TA: Langmuir Country: - |
Other Details:
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Languages: ENG Pagination: - Citation Subset: - |
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From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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