Abstract: TEM was used to study the film structure of “dry brush” and “wet brush” blending systems of polystyrenebpolyethylene oxidebpolystyrene (SEOS) and polyethylene oxide homopolymer (h-PEO). Results show that spherical PEO dispersed domains consisting of b-PEO and h-PEO can be observed in all of the four blending systems. With the increasing amount of homopolymer, the PEO domain size increases. When the mass fraction of the homopolymer in blends reaches 33.3%, the “core-shell” structure, similar to the micelles, can be clearly observed in the polystyrene (PS) matrix.