Molecular dynamics simulation of SDS and CTAB micellization and prediction of partition equilibria with COSMOmic

Journal
Langmuir : the ACS journal of surfaces and colloids  
Volume
29
Issue
37
Start Page
11582
End Page
11592
Citation
Langmuir 37 (29): 11582-11592 (2013)
Publisher DOI
10.1021/la402415b
Scopus ID
2-s2.0-84884260474
Publisher
ACS Publ.
Molecular dynamics (MD) simulations of the self-assembly of different ionic surfactants have been performed in order to obtain representative micellar structures. Subsequently, these structures were used to predict the partition behavior of various solutes in these micelles with COSMOmic, an extension of COSMO-RS. This paper includes multiple self-assembled micelles of SDS (sodium dodecyl sulfate, anionic surfactant) and CTAB (cetyltrimethylammoniumbromide, cationic surfactant) at different concentrations. Micellar size, density profiles, and shape (eccentricity) have been investigated. However, the size strongly depends on the functional definition of a micelle. For this reason, we present a method based on the free monomer concentration in aqueous solution as an optimization criterion for the micelle definition. The combination of MD with COSMOmic has the benefit of combining detailed atomistic information from MD with fast calculations of COSMOmic. For the first time the influence of micelle structure on pratition equilibria, predicted with COSMOmic, were investigated. In case of SDS more than 4600 and for CTAB more than 800 single micelles have been studied. The predictions of the partition coefficients with COSMOmic are in good agreement with experimental data. Additionally, the most favorable locations of selected molecules in the micelles as well as probable energy barriers are determined even for complex solutes such as toluene, propanolol, ephedrine, acetone, phenol, lidocaine, syringic acid, coumarin, isovanillin, ferulic acid, and vanillic acid. This method can therefore be applied as a potential screening tool for solutes (e.g., drugs) to find the optimal solute-surfactant combination. © 2013 American Chemical Society.
DDC Class
540: Chemie
More Funding Information
Deutsche Forschungsgemeinschaft, DFG
United States, Department of Energy, Office of Basic Energy Sciences