Diffusion in three and four component microemulsions containing nonionic surfactant studied by pulsed field gradient nuclear magnetic resonance and quasi-elastic light scattering

Abstract

Diffusion studies were performed with various methods to obtain some insight into the structure and the dynamical processes of three and four component microemulsions containing p-nonylphenol ethylene oxide adducts which were mixtures of highly branched p-nonyl isomers with well defined distributions of the ethylene oxide chain length.

Diffusion coefficients were determined by pulsed field gradient and pulsed field gradient Fourier transform¹ H NMR as well as by quasi-elastic light scattering.

The combined application of pulsed field gradient NMR and quasi-elastic light scattering gives information about the critical behaviour of the systems whereas pulsed field gradient Fourier transform NMR allows the determination of the diffusion coefficients of the individual constituents.

The results suggest that the very complex three and four component microemulsions studied undergo critical concentration fluctuations in a large temperature region from about 15 °C below the lower critical solution temperatures. The deduced critical exponents are in good agreement with theoretical predictions. The aggregates in the three and four component microemulsions show differences in the self diffusion behaviour of their constituents.