title: A model for monomer and micellar concentrations in surfactant solutions: application to conductivity, NMR, diffusion, and surface tension data.
abstract: An empirical model for the concentrations of monomeric and micellized surfactants in solution is presented as a consistent approach for the quantitative analysis of data obtained with different experimental techniques from surfactant solutions. The concentration model provides an objective definition of the critical micelle concentration (cmc) and yields precise and well defined values of derived physical parameters. The use of a general concentration model eliminates subjective graphical procedures, reduces methodological differences, and thus allows one to compare directly the results of different techniques or to perform global fits. The application and validity of the model are demonstrated with electrical conductivity, surface tension, NMR chemical shift, and self-diffusion coefficient data for the surfactants SDS, CTAB, DTAB, and LAS. In all cases, the derived models yield excellent fits of the data. It is also shown that there is no need to assume the existence of different premicellar species in order to explain the chemical shifts and self-diffusion coefficients of SDS as claimed recently by some authors.
authors.affiliation: Department of Physical Chemistry, Faculty of Science, University of Santiago de Compostela, E-27002 Lugo, Spain. wajih.al-soufi@usc.es
authors.forename: Wajih
authors.initials: W
authors.lastname: Al-Soufi
authors.forename: Lucas
authors.initials: L
authors.lastname: Piñeiro
authors.forename: Mercedes
authors.initials: M
authors.lastname: Novo
mesh_terms: D003198:Computer Simulation; D004058:Diffusion; D004553:Electric Conductivity; D008279:Magnetic Resonance Imaging; D009682:Magnetic Resonance Spectroscopy; D008823:Micelles; D008956:Models, Chemical; D017711:Nonlinear Dynamics; D012967:Sodium Dodecyl Sulfate / Q000032:analysis / Q000737:chemistry; D012996:Solutions / Q000737:chemistry*; D013223:Statistics as Topic / Q000379:methods; D013500:Surface Tension; D013501:Surface-Active Agents / Q000737:chemistry*
chemical_list: D008823:Micelles; D012996:Solutions; D013501:Surface-Active Agents; D012967:Sodium Dodecyl Sulfate