Aerosol-OT Reversed Micellar Formation at Low Water-Surfactant Ratio Studied by Synchrotron Radiation Small-Angle X-ray Scattering

Abstract

By using synchrontron radiation small-angle X-ray scattering, we have studied the structure of biologial buffer/ sodium bis(2-ethylhexy1)sulfosuccinate (AOT)/2,2,4-trimethylpentane (isooctane) reversed micelles with varying water-surfactant molar ratio 00 (=[H20]/[AOT]), AOT concentration, and temperature. The scattering data were analyzed by several methods, including a shell modeling. Although in a high (00 range (16 < 00 -= 50) the obtained structural parameters of the AOT reversed micelle and the linear relation between the'water pool radius and the wo value are mostly in agreement with those determined by other authors, for 0 < wo < 12, however, discrepancies were found. These deviations can be understood by a transient oligomerization of reversed micelles, where with the increase of water content the micellar oligomerization proceeds successively from a metastable oligomeric phase to a stable monomeric phase through a transient phase. Increasing the AOT concentration and/or temperature reduced the reverse micellar dimension.

Modeling the Self-Aggregation of Small AOT Reverse Micelles from First-Principles

“…In all three simulations, we find that for 15-24 % of the trajectory the RM's forms oligomers, in particular dimers, where the tails of two micelles are in bonding contact for a certain time. This finding agrees well with SAXS experiments 6,7 .…”

Selenium Nanoparticles: A Small-Angle Neutron Scattering Study

“…Eastoe et al 27 found a spherical to cylindrical structural transformation of the micelles and back again on the addition of increasing amounts of water; however, the micelles became spherical with the formation of PbS nanoclusters. 14 Hirai et al 24 suggest the presence of a small amount of reverse micellar oligomers and give a length of 12 Å for an AOT molecule, confirming that the shell consists of one layer of AOT molecules.…”

“…This corresponds to a spherical radius of 12.1 ( 0.4 Å, which agrees quite well with the results in the literature. 24 The molecular weight and hence the aggregation number can …”

Growth kinetics for AgI nanoparticles in AOT reverse micelles: Effect of molecular length of hydrocarbon solvents

“…The simultaneous presence in micellar solution of amorphous clusters and crystalline particles whose d is greater than d p (Fig. 2, curve 1) can be related to the presence in the system of the so-called 'oligomeric' phase [19,25] which represents the associates of interacting micelles. The smaller the micelle size, the greater is their number in such associates.…”