Physicochemical properties of micelles of poly(styrene-b-2-vinylpyridine-b-ethylene oxide) in aqueous solutions

Micelles of poly(styrene-b-2-vinylpyridine-b-ethylene oxide) (PS-b-P2VP-b-PEO) triblock copolymer were prepared in aqueous solutions. The physicochernical properties of the micelles were investigated by dynamic light scattering, zeta-potential measurements, atomic-force microscopy, and fluorescence spectroscopy. The micelles had an average diameter of about 200 nm under acidic conditions. The addition of dextran sulfate to a micellar solution under acidic conditions resulted in a significant decrease in the micelle size. This was due to a conformational change in the P2VP block form extended to shrunken forms after the cationic P2VP block was electrically neutralized with negative dextran sulfate. The release of anionic dye (Eosin Y) from the micelle particles was studied by a dialysis method, and proved to take tens of hours.