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pH sensitive polymer nanoparticles: effect of hydrophobicity on self-assembly
Sergey K Filippov1, Larisa Starovoytova, Cestmír Konák
1Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Heyrovsky Sq. 2, 162 06 Prague 6, Czech Republic. filippov@imc.cas.cz
Langmuir : the ACS Journal of Surfaces and Colloids
|August 28, 2010
Summary
Hydrophobicity influences pH-responsive polymer nanoparticle formation and stability. Surfactant hydrophilicity, not polymer hydrophobicity, dictates nanoparticle transformation and prevents aggregation.
Area of Science:
- Polymer Chemistry
- Nanotechnology
- Materials Science
Background:
- pH-responsive polymer nanoparticles are crucial for drug delivery and diagnostics.
- Understanding the role of hydrophobicity in nanoparticle formation is essential for controlled synthesis.
- Methacryloylated oligopeptide-based polymers offer tunable properties for nanostructure design.
Purpose of the Study:
- To investigate the influence of polymer hydrophobicity on pH-responsive nanoparticle formation and stability.
- To elucidate the mechanism of nanoparticle formation in polymer-surfactant systems across varying pH.
- To determine the role of surfactant hydrophilicity in controlling nanoparticle size and aggregation.
Main Methods:
- Dynamic Light Scattering (DLS) for size and stability analysis.
- Transmission Electron Microscopy (Cryo-TEM) for structural visualization.
- Nuclear Magnetic Resonance (NMR) for molecular interactions.
Main Results:
- Polyanions form hydrophobic domains in surfactant-free solutions at basic pH.
- Complex formation between polyanions and nonionic surfactants results in a pearl-necklace structure at high pH.
- Reversible nanoscale structures form below a critical pH (pH(tr)) for all systems studied.
Conclusions:
- Polymer hydrophobicity is critical for the initial pretransitional behavior of the polymer-surfactant complex.
- Once nanoparticle nuclei form, polymer hydrophobicity has a minor role in subsequent nanostructure behavior.
- Surfactant hydrophilicity, specifically the length of the poly(ethylene oxide) (PEO) chain, governs nanoparticle transformation and prevents aggregation via steric repulsion.
