Abstract:

In this paper we present the structural characterization of a five-component food-grade microemulsion contg. Tween 80, R(+)-limonene, ethanol, glycerol, and water. Our main approach to investigating the microstructure of dense microemulsions, and how it can be influenced by the various components, was to employ small-angle neutron scattering and the new evaluation technique for dense, interacting systems, the Generalized Indirect Fourier Transformation. We started our investigation with the impact of glycerol and ethanol on Tween 80 micelles in water. We found that glycerol increases the aggregation no. and withdraws the hydrating agents from the headgroup region of the surfactant, resulting in a higher packing d. of mols. in a micelle at slightly increasing size. The same trend holds when the micelles are oil swollen and/or ethanol is present. Ethanol, on the other hand, redistributes mainly between water and the interface-headgroup region of the surfactant. Part of it replaces surfactant mols. in the micelles, which increases the available interface and results in a higher no. of micelles with shrinking size. The same trend holds when the micelles are oil swollen and/or glycerol is present in the aq. phase. We also investigated samples along the diln. of a mixt. of surfactant and oil phase (R(+)-limonene and ethanol), which can be dild. with aq. phase (mixt. of water and glycerol) without the occurrence of phase sepn. In some samples of this diln. most probably bicontinuous structures are present. To elucidate this point, we also employed dynamic light scattering, viscosity, and cond. measurements. [on SciFinder(R)]