Characterization of polystyrene based diblock copolymer micelles

The micellization of polystyrene based block copolymers was investigated in aqueous and in organic media. Micelles formed from polystyrene-b-poly(sodium acrylate) (PS-b-PANa) in sodium chloride solutions were investigated by static light scattering (SLS). The aggregation numbers (N$rm sb{agg})$ were influenced by low salt concentrations ($<$0.10 M) and they were essentially independent of the soluble block lengths. The core radii ($rm sb{e}$ agreed well with previous solid state results on similar samples studied by small-angle X-ray scattering (SAXS). It was thus concluded that no supermicellar aggregates were present and that the cores were solvent free.A method to evaluate the critical micelle concentrations (cmc's) of block copolymer micelles by SLS was developed to account for the effects of polydispersity on the cmc. It was found that for block copolymers which have a significant dependence of the cmc on the insoluble block length and which are polydisperse only the present approach was able to evaluate the cmc.The micellization of PS-b-PANa and PS-b-poly(acrylic acid) (PS-b-PAA) block copolymers were investigated in organic solvents. The cmc's were found to range from $1 times10 sp{-7} { rm to} 5 times10 sp{-9}$ M for insoluble block lengths ranging from 2.6 to 18 units. The N$rm sb{agg}$ and R$rm sb{e}$ values for four PS-b-PANa series in tetrahydrofuran, were found to be a function of the length of both blocks. The effect of the degree of neutralization of the PAA block on micellization was probed by SLS and SAXS; micelle formation was found to commence at 5% neutralization. The distribution of water between toluene and the polar cores of block ionomer and sodium bis(2-ethylhexyl)sulfosuccinate (AOT) reverse micelles was investigated by proton chemical shift measurements as a function of temperature. The amount of water solubilized and the thermodynamic parameters of transfer were found to be a function of the core nature