Reversible aggregation of polystyrene-block-poly(2-vinylpyridine)-block-poly(ethylene oxide) block copolymer micelles in acidic aqueous Solutions.
Micelles of polystyrene-block-poly(2-vinylpyridine)-block-poly(ethylene oxide) (PS-PVP-PEO) were studied in acidic aqueous solutions by static and dynamic light scattering, alkalimetric titration, fluorescence correlation spectroscopy, and after deposition on a mica surface by atomic force microscopy. The PS-PVP-PEO micelles prepared by dialysis in ternary 1,4-dioxane-methanol-acidic water mixtures have a very low association number and show a strong tendency to form aggregates. The aggregation, which is promoted at low pH, seems to be fully reversible. Possible mechanisms of the aggregation are discussed. Atomic force microscopy scans of PS-PVP-PEO micelles deposited on a mica surface reveal the formation of micellar aggregates and support the general concept of aggregation upon changes in conditions and deterioration of the stability of small micelles.
Stepánek
Miroslav
M
Department of Physical and Macromolecular Chemistry, School of Science, Charles University in Prague, Czech Republic.
Matejícek
Pavel
P
Humpolícková
Jana
J
Procházka
Karel
K