DOSY is a recognized, efficient technique in the analysis of mixtures. It relies on the differences in self-diffusion coefficients,
which are determined by the molecular size. Nowadays, efforts are directed towards devising matrices able to interact with
the components of the mixture with differential affinity, and therefore capable to interfere with the diffusion processes and to
display resolving power towards species of close, or even equal molecular weight, like isomers. Usually, commercial nonionic
surfactants are mixtures of oligomeric species, since the head group, which is a short polyoxyehtylene chain, is somewhat
polydisperse. The embedment of Igepal CA-520, 5 polyoxyethylene iso-octylphenyl ether, in an inverse microemulsion led to
the separation of 1H signals of the various oligomeric components. This ensued from the differential partitioning between
the oil and the surface of the inverse micelles, which depends on the ethyleneoxide number (EON) of the head groups.
Thus, it was possible to ascertain that the length distribution of the polyethyleneoxide chains is ingood agreement with the
Poisson distribution theoretically predicted for the polymerization of ethylene oxide. The DOSY spectrum contributed to the
assignment of the signals and afforded the partition degree, between the two environments, for each individual oligomeric
species, providing further insight into nonionic inverse microemulsions, at present widely employed reaction media in the
nanotechnological syntheses.
