NMR chemical shifts and linewidth measurements were examined for mixtures of sodium 10-phenyldecanoate (Na x-PhDec) in deuterated aqueous solutions in the presence of varying compositions of poly(ethylene oxide) (PEO) polymers of 2000 and 4000 molecular weight. In addition, variable temperature NMR spectra and NMR spin lattice relaxation times (T 1 ) were obtained for the PEO-4000/Na x-PhDec system as a function of varying polymer concentrations. As expected, the polymer/surfactant systems exhibit the behaviour typical of that of an anionic surfactant/ neutral polymer system with well defined critical aggregation concentrations (CMC) corresponding to the formation of polymer/surfactant complexes below the CMC of the free surfactant. The 1 H-NMR linewidths acquired for the Na xPhDec/PEO-4000 system before and after the CMC region of the surfactant indicate that the maximum in the linewidth of the PEO proton peak is reached at approximately twice the CMC of the free surfactant. 2D-NMR NOESY measurements on this system exhibit cross peaks between the PEO protons and the protons on the surfactant backbone, consistent with the location of the phenyl group in the micellar interior. All these NMR experiments are interpreted in terms of the structure of the polymer/surfactant complexes as a function of the system composition.

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The micellization process of sodium 8-phenyloctanoate in a deuterated aqueous solution was studied, using 1H NMR spectroscopy and two-dimensional (2D) nuclear Overhauser enhancement spectroscopy (NOESY). 1H NMR spectra, acquired for the sodium 8-phenyloctanoate before and after the critical micelle concentration (CMC) value, showed that large chemical-shift changes were observed for both the aromatic proton peaks and the peaks for the methylene protons near the terminal phenyl group. The plots for the methylene protons near the headgroup do not show these large chemical-shift changes. These observations support the view that the terminal phenyl ring of the surfactant is primarily located in the micellar interior. The 2D NOESY experiments show significant cross-peaks, between the phenyl protons and the methylene protons of the surfactant, that substantiate the conclusions on those drawn from NMR aromatic solute induced shift (ASIS) experiments on the same and similar systems. All these observations are consistent with the Gruen model of the micelle and previous NMR NOESY experiments for other surfactant systems.Key words: surfactants, micelles, NMR, NOESY.