Structure Determination of a Highly Concentrated W/O Emulsion Using Pulsed-Field-Gradient Spin−Echo Nuclear Magnetic Resonance “Diffusion Diffractograms”

Diffraction-like effects have been observed by applying pulsed-field-gradient spin−echo (PFG-SE) NMR to a highly concentrated W/O emulsion, made from the nonionic surfactant C 12 E 4 (CH 3 (CH 2 ) 11 (OCH 2 CH 2 ) 4 OH), n -decane, and brine (1 wt % NaCl(aq) solution). The q -space plots of the PFG-SE NMR data show one pronounced maximum and the shoulder of a second maximum in the attenuation curve of the NMR signal of water. Such peaks are often referred to as diffraction-like peaks, because of the close analogy of their origin to the origin of peaks observed in scattering experiments. In this paper it is suggested that the peak positions in the “diffusion diffractograms” can be related to the structure of the emulsion, i.e., to the three-dimensional packing of the (nonspherical) emulsion droplets. Furthermore, the characteristic distances in the emulsion system, in this case related to the average size of an emulsion droplet, can be determined from the positions of the diffraction-like peaks. This can be achieved without the need to invoke models for the diffusion.