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Structural Study of Polystyrene-b-poly(acrylic acid) Micelles Complexed with Uranyl: A SAXS Core-Shell Model Analysis
Qiang Tian1, Di Zhang1, Na Li2
1State Key Laboratory of Environment-Friendly Energy Materials, School of Materials Science and Technology, Southwest University of Science and Technology, Mianyang 621010, China.
Langmuir : the ACS Journal of Surfaces and Colloids
|April 11, 2020
Summary
This study models humic acid colloids using polystyrene-block-poly(acrylic acid) micelles to understand uranyl ion interactions. Uranyl ions bind to micelles, shrinking their structure and causing destabilization at higher concentrations.
Area of Science:
- Colloid and Surface Science
- Environmental Chemistry
- Radiochemistry
Background:
- Interactions between natural colloidal organic matter and actinides are complex.
- Humic acid (HA) colloids play a crucial role in actinide sequestration, aggregation, and mobility.
- A model system is needed to elucidate these interactions.
Purpose of the Study:
- To model humic acid (HA) colloids using crew-cut polystyrene-block-poly(acrylic acid) (PS-b-PAA) micelles.
- To investigate the effects of uranyl ions on the structure and stability of these model colloids.
- To understand the sequestration and mobility mechanisms of HA colloids in the presence of actinides.
Main Methods:
- Synchrotron small-angle X-ray scattering (SAXS) was used to probe micelle structure.
- A core-shell model was applied to SAXS data, considering corona thickness and contrast changes.
- Transmission electron microscopy (TEM), dynamic light scattering (DLS), and zetametry were employed for complementary analysis.
Main Results:
- Uranyl ions exhibited a strong affinity for poly(acrylic acid) (PAA) segments in aqueous solution at pH 4-5.
- Uranyl adsorption induced shrinkage and improved contrast of the PAA corona.
- Colloidal destabilization was observed at high uranyl ion concentrations.
Conclusions:
- PS-b-PAA micelles effectively model HA colloids for studying actinide interactions.
- Uranyl ion binding significantly alters the structural and stability properties of these model colloids.
- The findings provide insights into the behavior of HA colloids in actinide-contaminated environments.
