| Abstract
| - The behavior of mixed poly(methacrylic acid)/poly(ethylene oxide) (PMA/PEO) shells of hybrid polymericmicelles with polystyrene cores was studied in detail by a combination of light scattering, fluorometric,potentiometric, and other techniques. The results show that the dissociation of poly(methacrylic acid) inthe inner layer close to the polystyrene core is suppressed, in part because of the relatively low polarityof the medium and because of a high concentration of carboxylic groups. The dissociation degree does notcorrespond to the bulk pH. The PMA chains form a hydrogen-bond-stabilized interpolymer complex withPEO chains in the inner shell. The compact layer of the PMA−PEO complex around the polystyrene coreis very stable and resistant to changes in the bulk solvent properties. Potentiometric titration shows thatan important fraction of PMA, which is engaged in the complex formation, cannot be neutralized even ina considerable excess of the base. The peripheral part of the layer is formed preferentially by the stretchedand ionized free ends of the PMA blocks. Hybrid PS−(PMA/PEO) micelles resemble so-called “onion type”micelles, for example, polystyrene-block-poly(2-vinylpyridine-block-poly(ethylene oxide)) [see: Procházkaet al. Macromolecules1996, 29, 6526.] and may be regarded as “pseudo-multilayer” polymeric nanoparticles.
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