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

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.