Artículos de revistas
Molecular dynamics simulations of AOT-water/formamide reverse micelles: Structural and dynamical properties
Registro en:
Journal Of Chemical Physics. Amer Inst Physics, v. 129, n. 24, 2008.
0021-9606
WOS:000262226800027
10.1063/1.3042275
Autor
Pomata, MHH
Laria, D
Skaf, MS
Elola, MD
Institución
Resumen
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) 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 similar to 15 A, while the corresponding polar solvent-to-surfactant molar ratios were intermediate between w(0)=4.3 for FM and w(0)=7 for W. The resulting overall shapes of the micelles resemble distorted ellipsoids, with average eccentricities of the order of similar to 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 similar to 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. 129 24 CONICET (Argentina) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)