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What causes the anomalous aggregation in pluronic aqueous solutions?
Kuo-Chih Shih1, Zhiqiang Shen, Ying Li
1Department of Agricultural Chemistry, National Taiwan University, Taipei, 10617, Taiwan. hmlai@ntu.edu.tw.
Soft Matter
|September 4, 2018
Summary
Pluronic block copolymers form large aggregates below their critical micelle concentration. Acids and bases suppress this aggregation by altering molecular interactions and solubility.
Area of Science:
- Polymer Science
- Materials Science
- Physical Chemistry
Background:
- Pluronic (PL) block copolymers are versatile materials used in drug delivery, templating, and rheology modification.
- Typically, surfactants form micelles above a critical micelle concentration (CMC), but PL copolymers exhibit unique aggregation behavior.
Purpose of the Study:
- To investigate the formation of anomalous large Pluronic aggregates below the CMC.
- To understand the structural characteristics and influencing factors of these aggregates.
Main Methods:
- Dynamic light scattering (DLS) and small-angle X-ray/neutron scattering (SAXS/SANS) were employed for structural characterization.
- Molecular dynamics (MD) simulations were utilized to probe the interaction mechanisms.
Main Results:
- Anomalous large Pluronic aggregates were observed below the CMC for F108, F127, F88, and P84.
- Molecular dynamics simulations indicated that the weakly hydrophobic PPO segments drive aggregate formation.
- Addition of acids or bases to F108 solutions significantly suppressed aggregate formation for extended periods.
Conclusions:
- Pluronic block copolymers exhibit unique aggregation behavior below the CMC, driven by PPO segment interactions.
- The addition of acids or bases effectively controls Pluronic aggregate formation through electrostatic repulsion and salting-out effects.
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