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

Autores
<div class="autor_fcen" id="6837">Pomata, M.H.H.</div>; <div class="autor_fcen" id="4817">Laria, D.</div>; Skaf, M.S.; <div class="autor_fcen" id="2789">Elola, M.D.</div>
Año de publicación
2008
Idioma
inglés
Tipo de recurso
artículo
Estado
Versión publicada
Descripción
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.
Fuente
J Chem Phys 2008;129(24)
Materia
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
Nivel de accesibilidad
Acceso abierto
Licencia
http://creativecommons.org/licenses/by/2.5/ar
Repositorio
Biblioteca Digital (UBA-FCEN)
Institución
Universidad Nacional de Buenos Aires. Facultad de Ciencias Exactas y Naturales
OAI Identificador
snrd:HASH01aa92399e55dea3d9e63bc7