Polystyrene-block-poly(ethylene oxide) micelles in aqueous solution

The formation of micelles, micellar clusters, and aggregates in aqueous sol utions of polystyrene-block-poly(ethylene oxide) macromolecules (PS-b-PEO) in the presence of various additives is studied. Behavior of the PS-b-PEO m icellar solutions is examined with static light scattering and sedimentatio n in the ultracentrifuge. Sedimentograms of the solution of PS-b-PEO in wat er 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). Experimenta l data show that the weight fraction of micelles and micellar clusters in t he 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 g lassy polystyrene cores, decomposes the micellar clusters due to an increas e of mobility of macromolecules forming micelles. Addition of inorganic sal ts interacting with poly(ethylene oxide) tails also results in the disappea rance of micellar clusters, Alcohols introduced as cosolvents can strongly change the morphology of the amphiphilic PS-b-PEO micelles.