Effect of stabilizer on formation of "onionlike" multilayered polystyrene-block-poly(methyl methacrylate) particles

The effect of the kind of stabilizers on the formation of "onionlike" multilayered polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) particles was studied. The release of toluene from PS-b-PMMA/toluene droplets dispersed in aqueous medium resulted in the formation of onionlike multilayered structures in the particles for all stabilizers used. However, the surface composition of the particles was strongly affected by the kind of stabilizer. When sodium dodecyl sulfate (SDS) and poly(vinyl alcohol) (PVA) were used as stabilizers, the surface of the particles was occupied by PMMA phase. On the other hand, in the cases of Emulgen 911 (polyoxyethylene nonylphenyl ether) and Tween 80 (polyoxyethylene sorbitan monooleate) as stabilizers, the PS phase occupied the surfaces. These results for SDS, PVA, and Emulgen 911 are consistent with the surface layer of the PS-b-PMMA particles being occupied by the polymer phase, which gives a lower interfacial tension than that of another phase. However, in the case of Tween 80, interfacial tensions between water and toluene solutions of the polymer showed almost the same values making it impossible to predict the surface polymer phase.