Polystyrene-block-Poly(ethylene oxide) Micelles in Aqueous Solution

The formation of micelles, micellar clusters, and aggregates in aqueous solutions of polystyrene- block -poly(ethylene oxide) macromolecules (PS- b -PEO) in the presence of various additives is studied. Behavior of the PS- b -PEO micellar solutions is examined with static light scattering and sedimentation in the ultracentrifuge. Sedimentograms of the solution of PS- b -PEO in water exhibit two peaks which correspond to the formation of single micelles ( R g = 12.8 nm) and secondary micellar clusters ( R g = 42.1 nm). Experimental data show that the weight fraction of micelles and micellar clusters in the solution strongly depends on the chemical composition of the dispersing media. The addition of 1.5 vol % toluene, which is a good solvent for the glassy polystyrene cores, decomposes the micellar clusters due to an increase of mobility of macromolecules forming micelles. Addition of inorganic salts interacting with poly(ethylene oxide) tails also results in the disappearance of micellar clusters. Alcohols introduced as cosolvents can strongly change the morphology of the amphiphilic PS- b -PEO micelles.