Molecular dynamics simulations of AOT-water/formamide reverse micelles: Structural and dynamical properties

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We present results from molecular dynamics simulations performed on reverse micelles immersed in cyclohexane. Three different inner polar phases are considered: water (W), formamide (FM), and an equimolar mixture of the two solvents. In all cases, the surfactant was sodium bis(2-ethylhexyl) sulfosuc...

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Autores principales:	Pomata, M.H.H., Laria, D., Skaf, M.S., Elola, M.D.
Formato:	Artículo publishedVersion
Lenguaje:	Inglés
Publicado:	2008
Materias:	Amides Colloids Dynamics Hydrogen Hydrogen bonds Ionization of liquids Molecular dynamics Quantum chemistry Sodium Solvents Surface active agents Average numbers Characteristic times Dipole orientations Dynamical properties Equimolar mixtures Head groups Ionic species Length scales Life-times Local densities Molar ratios Molecular dynamics simulations Polar phasis Polar solvents Preferential solvations Radial directions Reverse micelles Rotational modes Rotational motions Sulfosuccinate Surfactant layers Micelles
Acceso en línea:	http://hdl.handle.net/20.500.12110/paper_00219606_v129_n24_p_Pomata
Aporte de:	Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) de Universidad de Buenos Aires

id	paperaa:paper_00219606_v129_n24_p_Pomata
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spelling	paperaa:paper_00219606_v129_n24_p_Pomata2023-06-12T16:43:19Z Molecular dynamics simulations of AOT-water/formamide reverse micelles: Structural and dynamical properties J Chem Phys 2008;129(24) Pomata, M.H.H. Laria, D. Skaf, M.S. Elola, M.D. Amides Colloids Dynamics Hydrogen Hydrogen bonds Ionization of liquids Molecular dynamics Quantum chemistry Sodium Solvents Surface active agents Average numbers Characteristic times Dipole orientations Dynamical properties Equimolar mixtures Head groups Ionic species Length scales Life-times Local densities Molar ratios Molecular dynamics simulations Polar phasis Polar solvents Preferential solvations Radial directions Reverse micelles Rotational modes Rotational motions Sulfosuccinate Surfactant layers Micelles We present results from molecular dynamics simulations performed on reverse micelles immersed in cyclohexane. Three different inner polar phases are considered: water (W), formamide (FM), and an equimolar mixture of the two solvents. In all cases, the surfactant was sodium bis(2-ethylhexyl) sulfosuccinate (usually known as AOT). The initial radii of the micelles were R∼15 Å, while the corresponding polar solvent-to-surfactant molar ratios were intermediate between w0 =4.3 for FM and w0 =7 for W. The resulting overall shapes of the micelles resemble distorted ellipsoids, with average eccentricities of the order of ∼0.75. Moreover, the pattern of the surfactant layer separating the inner pool from the non-polar phase looks highly irregular, with a roughness characterized by length scales comparable to the micelle radii. Solvent dipole orientation polarization along radial directions exhibit steady growths as one moves from central positions toward head group locations. Local density correlations within the micelles indicate preferential solvation of sodium ionic species by water, in contrast to the behavior found in bulk equimolar mixtures. Still, a sizable fraction of ∼90% of Na+ remains associated with the head groups. Compared to bulk results, the translational and rotational modes of the confined solvents exhibit important retardations, most notably those operated in rotational motions where the characteristic time scales may be up to 50 times larger. Modifications of the intramolecular connectivity expressed in terms of the average number of hydrogen bonds and their lifetimes are also discussed. © 2008 American Institute of Physics. Fil:Pomata, M.H.H. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. Fil:Laria, D. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. Fil:Elola, M.D. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. 2008 info:eu-repo/semantics/article info:ar-repo/semantics/artículo info:eu-repo/semantics/publishedVersion application/pdf eng info:eu-repo/semantics/openAccess http://creativecommons.org/licenses/by/2.5/ar http://hdl.handle.net/20.500.12110/paper_00219606_v129_n24_p_Pomata
institution	Universidad de Buenos Aires
institution_str	I-28
repository_str	R-134
collection	Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA)
language	Inglés
orig_language_str_mv	eng
topic	Amides Colloids Dynamics Hydrogen Hydrogen bonds Ionization of liquids Molecular dynamics Quantum chemistry Sodium Solvents Surface active agents Average numbers Characteristic times Dipole orientations Dynamical properties Equimolar mixtures Head groups Ionic species Length scales Life-times Local densities Molar ratios Molecular dynamics simulations Polar phasis Polar solvents Preferential solvations Radial directions Reverse micelles Rotational modes Rotational motions Sulfosuccinate Surfactant layers Micelles
spellingShingle	Amides Colloids Dynamics Hydrogen Hydrogen bonds Ionization of liquids Molecular dynamics Quantum chemistry Sodium Solvents Surface active agents Average numbers Characteristic times Dipole orientations Dynamical properties Equimolar mixtures Head groups Ionic species Length scales Life-times Local densities Molar ratios Molecular dynamics simulations Polar phasis Polar solvents Preferential solvations Radial directions Reverse micelles Rotational modes Rotational motions Sulfosuccinate Surfactant layers Micelles Pomata, M.H.H. Laria, D. Skaf, M.S. Elola, M.D. Molecular dynamics simulations of AOT-water/formamide reverse micelles: Structural and dynamical properties
topic_facet	Amides Colloids Dynamics Hydrogen Hydrogen bonds Ionization of liquids Molecular dynamics Quantum chemistry Sodium Solvents Surface active agents Average numbers Characteristic times Dipole orientations Dynamical properties Equimolar mixtures Head groups Ionic species Length scales Life-times Local densities Molar ratios Molecular dynamics simulations Polar phasis Polar solvents Preferential solvations Radial directions Reverse micelles Rotational modes Rotational motions Sulfosuccinate Surfactant layers Micelles
description	We present results from molecular dynamics simulations performed on reverse micelles immersed in cyclohexane. Three different inner polar phases are considered: water (W), formamide (FM), and an equimolar mixture of the two solvents. In all cases, the surfactant was sodium bis(2-ethylhexyl) sulfosuccinate (usually known as AOT). The initial radii of the micelles were R∼15 Å, while the corresponding polar solvent-to-surfactant molar ratios were intermediate between w0 =4.3 for FM and w0 =7 for W. The resulting overall shapes of the micelles resemble distorted ellipsoids, with average eccentricities of the order of ∼0.75. Moreover, the pattern of the surfactant layer separating the inner pool from the non-polar phase looks highly irregular, with a roughness characterized by length scales comparable to the micelle radii. Solvent dipole orientation polarization along radial directions exhibit steady growths as one moves from central positions toward head group locations. Local density correlations within the micelles indicate preferential solvation of sodium ionic species by water, in contrast to the behavior found in bulk equimolar mixtures. Still, a sizable fraction of ∼90% of Na+ remains associated with the head groups. Compared to bulk results, the translational and rotational modes of the confined solvents exhibit important retardations, most notably those operated in rotational motions where the characteristic time scales may be up to 50 times larger. Modifications of the intramolecular connectivity expressed in terms of the average number of hydrogen bonds and their lifetimes are also discussed. © 2008 American Institute of Physics.
format	Artículo Artículo publishedVersion
author	Pomata, M.H.H. Laria, D. Skaf, M.S. Elola, M.D.
author_facet	Pomata, M.H.H. Laria, D. Skaf, M.S. Elola, M.D.
author_sort	Pomata, M.H.H.
title	Molecular dynamics simulations of AOT-water/formamide reverse micelles: Structural and dynamical properties
title_short	Molecular dynamics simulations of AOT-water/formamide reverse micelles: Structural and dynamical properties
title_full	Molecular dynamics simulations of AOT-water/formamide reverse micelles: Structural and dynamical properties
title_fullStr	Molecular dynamics simulations of AOT-water/formamide reverse micelles: Structural and dynamical properties
title_full_unstemmed	Molecular dynamics simulations of AOT-water/formamide reverse micelles: Structural and dynamical properties
title_sort	molecular dynamics simulations of aot-water/formamide reverse micelles: structural and dynamical properties
publishDate	2008
url	http://hdl.handle.net/20.500.12110/paper_00219606_v129_n24_p_Pomata
work_keys_str_mv	AT pomatamhh moleculardynamicssimulationsofaotwaterformamidereversemicellesstructuralanddynamicalproperties AT lariad moleculardynamicssimulationsofaotwaterformamidereversemicellesstructuralanddynamicalproperties AT skafms moleculardynamicssimulationsofaotwaterformamidereversemicellesstructuralanddynamicalproperties AT elolamd moleculardynamicssimulationsofaotwaterformamidereversemicellesstructuralanddynamicalproperties
_version_	1769810272028983296

Molecular dynamics simulations of AOT-water/formamide reverse micelles: Structural and dynamical properties

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