Four-Component Micellar Model for Small-Angle Scattering Applications:  A SANS Study of the Core and Counterion Profiles of Sodium Alkyl Sulfate Micelles

Abstract

Multishell models used for calculating the elementary scattering amplitude from micelles are replaced by the Fourier transforms of the probability density functions of finding the hydrophobic (methyl and methylene) groups as well as the headgroup and counterions at a particular distance from the micellar center. Model variables are the aggregation number and two width parameters respectively characterizing the Gaussian core and the exponential counterion profiles. Application of the model to almost spherical sodium nonyl-, decyl and undecyl sulfate micelles leads to reasonable best-fit values. Aggregation numbers are tested by a recent thermodynamic model of micellization. Within the limits set by the finite resolution of the method, the group-density functions render possible to determine the spatial distribution of any physical quantity inside and around the micelles that depends only on the number of the molecular groups present. As an example, the relative dielectric permittivity is discussed.

Instrumental developments for anomalous small-angle X-ray scattering from soft matter systems

“…In the scattering model, the micelles are represented by core-double-shell-type spherical objects (Vass, 2001). Fig.…”

Size, Hydration, and Shape of SDS/Heptane Micelles Investigated by Time-Resolved Fluorescence Quenching and Electron Spin Resonance

“…Therefore, V shell may also be written as or equivalently The volume per headgroup V hg includes the headgroup volume plus a fraction of the volume of a counterion. The volume contributions from the counterions, and the apparent equivalence of hydration water and free water, have been discussed. , In our calculations the polar shell thickness, s , is set to be 5 Å, a value that fits the small-angle neutron scattering data, , the sulfur atom density distribution obtained in an MD simulation, and the size of the sulfate group. Then letting V hg = 66 Å 3 (the volume of the sulfate ion), V shell may be obtained from eqs 4−6 and hence the fraction f from eq 9.…”

A molecular dynamics investigation of structure and dynamics of SDS and SDBS micelles

“…For over a hundred years, surfactants have been exploited in industrial processes such as detergency, lubrication, corrosion, colloid stabilization, drug-delivery, etc. [1][2][3] Surfactants have been extensively studied in order to determine the nature of their organized structure and the associated dynamics using a variety of experimental techniques that ranged from NMR, [4][5][6] to EPR, 6,7 light scattering, 8,9 small angle neutron scattering [10][11][12] and time resolved fluorescence spectroscopy. 13,14 A central topic in their chemistry is the understanding of the physical properties of micelles, both from the perspective of organized assemblies and for their use as solvating agents.…”