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Lateral dynamics of surfactants at the free water surface. A computer simulation study.
MedLine Citation:
PMID:  23016629     Owner:  NLM     Status:  Publisher    
Abstract/OtherAbstract:
Molecular dynamics simulations of the adsorption layer of five different surfactant molecules, i.e., pentyl alcohol, octyl alcohol, dodecyl alcohol, sodium dodecyl sulfate and dodecyl trimethyl ammonium chloride are performed at the free surface of their aqueous solution at two surface densities, namely 1 and 4 μmol/m2 at 298 K. The results are analyzed in terms of the two dimensional single molecule dynamics, in particlular, lateral diffusion of the surfactants at the liquid surface, in order to distinguish between two possible adsorption scenarios, namely the assumptions of localized and mobile surfactants. The obtained results, in accordance with the dynamical nature of the liquid phase and liquid surface, clearly support the latter scenario, as the time scale of lateral diffusion of the surfactant molecules is found to be comparable with that of the three dimensional diffusion of water in the bulk liquid phase. The mechanism of this lateral diffusion is also investigated in detail by calculating binding energy distribution of the water molecules in the first hydration shell of the surfactant headgroups and that of the non-first shell surface waters, and by calculating the mean residence time of the water molecules in the first hydration shell of the surfactant headgroups. This time is found to be at least an order of magnitude smaller than the characteristic time of the lateral diffusion of the surfactants, revealing that surfactant molecules move without their first shell hydration water neighbors at the surface.
Authors:
Nóra Abrankó Rideg; Maria Darvas; Imre Varga; Pal Jedlovszky
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2012-9-27
Journal Detail:
Title:  Langmuir : the ACS journal of surfaces and colloids     Volume:  -     ISSN:  1520-5827     ISO Abbreviation:  Langmuir     Publication Date:  2012 Sep 
Date Detail:
Created Date:  2012-9-28     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  9882736     Medline TA:  Langmuir     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
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