Structure of water-based ferrofluids with sodium oleate and polyethylene glycol stabilization by small-angle neutron scattering: contrast-variation experiments

Abstract

Contrast variation in small‐angle neutron scattering (SANS) experiments is used to compare the structures of a water‐based ferrofluid, where magnetite nanoparticles are stabilized by sodium oleate, and its mixture with biocompatible polyethylene glycol, PEG. The basic functions approach is applied, which takes into account the effects of polydispersity and magnetic scattering. Different types of stable aggregates of colloidal particles are revealed in both fluids. The addition of PEG results in a reorganization of the structure of the aggregates: the initial comparatively small and compact aggregates (about 40 nm in size) are replaced by large (more than 120 nm in size) fractal‐type structures. It is postulated that these large structures are composed of single magnetite particles coated with PEG, which replaces sodium oleate. Micelle formation involving free sodium oleate is observed in both fluids. The structures of the fluids remain unchanged with increasing temperature up to 343 K. New and specific possibilities of SANS contrast variation with respect to multicomponent systems with different aggregates are considered.

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

“…The obtained results are consistent with the analysis of the interaction of PEG with SO-coated magnetite nanoparticles in water-based magnetic fluids [8], where the structure reorganization of the particle aggregates at sufficiently high PEG content was explained by the formation of the "polymer layer" around colloidal particles as a result of partial replacement of SO with PEG on the surface of magnetite.…”

“…Here, we are concerned with the interaction of PEG with SO micelles in water under the conditions characteristic for the previously studied magnetic fluids [8]. Specifically, we investigated aqueous micelle solutions of SO in a concentration range of 1 -8.5 wt.…”

“…It was probed as a drug carrier itself [5]. There is a well-proven technique to produce aqueous suspensions of magnetic nanoparticles coated with SO layers [6][7][8][9] known as magnetic fluids. Recently, it was shown [10;11] that the biocompatibility of SO-stabilized magnetic fluids can be improved through the introduction in their structure of a biocompatible water-soluble polymer, polyethylene glycol (PEG), H(OCH 2 -CH 2 ) n OH.…”

SANS Study of Poly(ethylene glycol) Solutions in D2O

“…The scattering form factor of the coils is well described by the Debye formula over the whole measured q-interval at the PEG concentration below 2%. High adsorption properties of PEG for various substrates [5][6][7] and nanoparticles [8] also suggest a developed structure of this polymer.…”

Effect of the Molecular Weight of Poly(ethylene glycol) on the Properties of Biocompatible Magnetic Fluids

“…A magnetic fluid-magnetite particles coated with sodium oleate and PEG-was formed in this way [8]. Infrared spectroscopy and digital scanning calorimetry measurements showed that after such a procedure, PEG adsorbs on the magnetite [8,9]. All samples contained the same amount of PEG-20.69 mg per mL of magnetic fluid.…”