Diffraction-like effects in a highly concentrated w/o emulsion: a PFG NMR study

Diffraction-like effects have been observed by applying pulsed field gradient (PFG) nuclear magnetic resonance (NMR) to a highly concentrated water-in-oil (W/O) emulsion, made up of the nonionic surfactant C12E4 [CH3(CH2)11(OCH2CH2)4OH], n-decane, and brine [1 wt% NaCl(aq) solution]. The pulsed field gradient NMR data show one pronounced maximum and the shoulder of a second maximum in the attenuation curve of the NMR signal from water, the so-called Bragg interference peaks. From the diffraction-like peaks, the average distance (center to center) between the emulsion droplets can be obtained, in this case related to the average size of an emulsion droplet. Furthermore, we note that the long-term stability of the emulsion can be followed by pulsed field gradient NMR.