1H-NMR of reverse micelles. I: The surfactant resonances as probes for the AOT/water/isooctane system.

1H-NMR spectra of Aerosol-OT (AOT) reverse micelles in isooctane are reported at various water contents and several temperatures. The resonances from the AOT protons near the polar head are completely assigned. The NMR parameters (chemical shift and linewidth) appear to be suitable probes for characterizing the physico-chemical state of micelles, in particular in order to define the range in which the system is fully homogeneous and transparent. The results correlate well with those obtained from optical density measurements. Lanthanide ions dissolved in the water phase selectively perturb the AOT resonances from the protons nearest to the polar head; conversely, non-polar shift reagents soluble in the organic phase do not cause appreciable effects on any of the observable signals.