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Structure and energetics of model amphiphilic molecules at the water liquid-vapor interface - A molecular dynamics studyA molecular dynamics study of adsorption of p-n-pentylphenol at infinite dilution at the water liquid-vapor interface is reported. The calculated free energy of adsorption is -8.8 +/- 0.7 kcal/mol, in good agreement with the experimental value of -7.3 kcal/mol. The transition between the interfacial region and the bulk solution is sharp and well-defined by energetic, conformational, and orientational criteria. At the water surface, the phenol head group is mostly immersed in aqueous solvent. The most frequent orientation of the hydrocarbon tail is parallel to the interface, due to dispersion interactions with the water surface. This arrangement of the phenol ring and the alkyl chain requires that the chain exhibits a kink. As the polar head group is being moved into the solvent, the chain length increases and the tail becomes increasingly aligned toward the surface normal, such that the nonpolar part of the molecule exposed to water is minimized. The same effect was achieved when phenol was replaced by a more polar head group, phenolate.
Document ID
19930060920
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Pohorille, Andrew
(California Univ., San Francisco; NASA, Ames Research Center Moffett Field, CA, United States)
Benjamin, Ilan
(California Univ. Santa Cruz, United States)
Date Acquired
August 16, 2013
Publication Date
January 1, 1993
Publication Information
Publication: Journal of Physical Chemistry
Volume: 97
Issue: 11
ISSN: 0022-3654
Subject Category
Inorganic And Physical Chemistry
Accession Number
93A44917
Funding Number(s)
CONTRACT_GRANT: NCA2-315
CONTRACT_GRANT: NSF CHE-90-15106
Distribution Limits
Public
Copyright
Other

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