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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.

Amphiphilic multimolecular block copolymer micelles of polystyrene-block-poly(methacrylic acid) and polystyrene-block-poly(ethylene oxide) were investigated by fluorescence correlation spectroscopy (FCS) in aqueous media using octadecylrhodamine B (ORB) as a micelle-specific probe, together with UV−visible absorption and other fluorescence techniques (steady-state spectroscopy and depolarization and time-resolved fluorescence decay measurements). The aim of the study was to show that the fluorescence techniques alone provide sufficient information on the micellar system, allowing, thus, for the fully conclusive study. Other techniques, such as static and quasi-elastic light scattering and atomic force microscopy were used just for comparison to prove the reliability of the FCS results and estimate their accuracy. The binding kinetics of ORB to micelles in aqueous solutions accompanied by association-dependent changes in UV−vis and fluorescence spectra and the binding equilibrium were also studied because knowledge of them is necessary for the correct interpretation of the FCS results.