Emulsions: A time-saving evaluation of the droplets' polydispersity and ofthe dispersed phase self-diffusion coefficient

The NMR pulsed magnetic field-gradient spin-echo (PGSE) technique is used t o study restricted diffusion in emulsion droplets. Experimental and theoret ical difficulties are discussed. A limiting law for evaluating the self-dif fusion coefficient directly from the data is derived. For the polydispersed system, the methods allow us also to obtain information about the droplet size distribution. The reliability of the polynomial representation of simu lated and experimental data is investigated, with emphasis on the applicati on to emulsion. Experimental results are given for the water-in-oil system formed by water-swollen Sephadex G-50 and cyclohexane at 25 degrees C. The agreement between the self-diffusion calculated and that measured in water- Sephadex is quite good.