Collect. Czech. Chem. Commun. 2003, 68, 2120-2138

Light Scattering, Atomic Force Microscopy and Fluorescence Correlation Spectroscopy Studies of Polystyrene-block-poly(2-vinylpyridine)-block-poly(ethylene oxide) Micelles

Miroslav Štěpáneka, Jana Humpolíčkováa, Karel Procházkaa,*, Martin Hofb, Zdeněk Tuzarc, Milena Špírkovác and Thomas Wolffd

a Department of Physical and Macromolecular Chemistry and Laboratory of Specialty Polymers, Faculty of Science, Charles University, Albertov 6, 128 43 Prague 2, Czech Republic
b J. Heyrovský Institute of Physical Chemistry, Academy of Sciences of the Czech Republic and Center for Complex Molecular Systems and Biomacromolecules, Dolejškova 3, 182 23 Prague 8, Czech Republic
c Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Heyrovského nám. 2, 162 06 Prague 6, Czech Republic
d Institute of Physical Chemistry and Electrochemistry, Dresden Technical University, Mommsenstrasse 13, 01062 Dresden, Germany


Polymeric nanoparticles formed by triblock copolymer polystyrene-block-poly(2-vinylpyridine)-block-poly(ethylene oxide), PS-PVP-PEO, in aqueous media were studied by a combination of fluorescence correlation spectroscopy with other fluorescence techniques, light scattering and atomic force microscopy. The studied polymeric nanoparticles exist in the form of (i) core/shell micelles in acid solution at pH lower than 4.8 and (ii) three-layer onion micelles at higher pH. Since water is a very strong precipitant for PS, both types of micelles have kinetically frozen spherical PS cores. The cores of micelles in acid media are surrounded by soluble shells formed by partly protonated PVP and PEO, while the cores of micelles in alkaline media are surrounded by compact insoluble layers of deprotonated PVP and soluble PEO shells. The micellization behavior of PS-PVP-PEO micelles is accompanied by secondary aggregation of micelles, which is provoked by stirring, shaking and also by filtration of micellar solutions. Therefore fluorescence correlation spectroscopy (FCS), which, in contrast to light scattering techniques, does not require filtration, was used as the main experimental technique for the characterization of non-aggregated micelles. The binding of a fluorescence probe, octadecylrhodamine B (ORB), to polymeric micelles, was studied before the FCS study of micelles.

Keywords: Block copolymer micelles; Onion micelles; Water-soluble polymers; Polystyrene; Poly(2-vinylpyridine); Poly(ethylene oxide); Octadecylrhodamine B; Light scattering; Fluorescence; Fluorescence correlation spectroscopy; Atomic force microscopy.

References: 58 live references.