Impact of polyethylene glycol on aqueous micellar solutions of sodium oleate studied by small-angle neutron scattering

• Structure and interaction parameters of micelles with and without PEG were obtained.
• PEG addition changes power-law type behaviour of the micelles aggregation number.
• Complicated sensitivity of other parameters of micelle to the PEG presence was concluded.
• Screening effect of micelle interaction takes place at high PEG addition.
• Polymer adsorbs on the micelle surface or even micelles are wrapped by some part of the polymer.

The structure and interaction parameters of micelles in solutions of anionic surfactant sodium oleate (SO) in deuterated water were studied by small-angle neutron scattering. The effect of addition of polymer, polyethylene glycol (PEG), on micelle solutions was investigated. The dependences of the micelle aggregation number, degree of ionization, axial ratio, average size, charge, inverse screening length, surface potential on the surfactant concentration with and without PEG in the solutions were obtained and analyzed. A change in the power-law type behaviour of the aggregation number on the SO concentration was observed at 2 wt.% of PEG in the surfactant/polymer mixtures. The screening effect with respect to the micelle interaction took place on addition of a large amount of PEG (about 10 wt.% in the mixture). The obtained results are particularly important for understanding the structure reorganization effect on addition of biocompatible PEG to water-based magnetic fluids stabilized by SO.

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