B. Derecskei et al., Atomic-level molecular modeling of AOT reverse micelles. 1. The AOT molecule in water and carbon tetrachloride, LANGMUIR, 15(6), 1999, pp. 1981-1992
The anionic surfactant bis(2-ethylhexyl) sodium sulfosuccinate (Aerosol OT
or AOT) is studied by atomic-level molecular modeling, using the second-gen
eration ESFF (extensible systematic force field). The geometries of seven r
epresentative conformers are analyzed. The energies of these conformers cor
respond to those of the most probable ones based on random-sampling statist
ics and differ by, at most, 10 kcal/mol. Thus, these conformers should be a
vailable for the system under typical ambient conditions. Interactions with
water and carbon tetrachloride modify the geometries only to a modest exte
nt. The solvation by water is found to be exoergic, and the analysis of ind
ividual AOT-water interactions identified four strongly bound water molecul
es (with >10 kcal/mol of interaction energy), in accordance with experiment
al results. A CCl4 box was generated for the investigation of the effects o
f carbon tetrachloride as a solvent. A truncated-cone-geometry model of the
AOT molecule yields 14.5 as the estimated aggregation number N of AOT reve
rse micelles in CCl4 in good agreement with the experimental value of the m
ean aggregation, [n] = 15-17, of the solution. The predicted diameter of th
e dry reverse! micelles d = 2.8 nm is comparable with the experimental appa
rent hydrodynamic diameter, [D-h] = 3 2 am (at w(o) = 0.8).