| Abstract
| - The self-aggregation and supramolecular micellar structure of twosurfactants in aqueous solution, the anionic surfactant SDP2S (sodiumdodecyl dioxyethylene-2 sulfate) and the nonionic surfactant TritonX-100 (octylphenol-polyoxyethylene ether with 9.5 ethoxy groups),were investigated by NMR spectroscopy. The critical micellar concentration(CMC), the size, and shape of the aggregates were determined by diffusionordered NMR spectroscopy (DOSY), while 2D NOESY NMR spectra were usedto study the mutual spatial arrangement of surfactant molecules inthe aggregated state. A nonlinear increase of the micellar hydrodynamicradius, indicating possible sphere-to-rod shape transition, was foundfor SDP2S at higher surfactant concentrations. Triton X-100 micelleswere found to be almost spherical at low surfactant concentrations,but formation of ellipsoid shaped particles and/or micellar aggregationwas observed at higher concentrations. The NOESY data show that atlow concentration Triton X-100 forms a two-layer spherical structurein the micelles, with partially overlapping internal and externallayers of Triton X-100 molecules and no distinct hydrophilic−hydrophobicboundary.
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