Synthesis of block copolymers is of great interest due to their abilities to self-assemble into a variety of structured, ordered, or partially ordered morphologies, and because they have number of applications. Three samples of poly(styrene)-block-poly(ethylene oxide) (PS-b-PEO) were synthesized by employed atom transfer radical polymerization (ATRP) technique and using monofunctional PEO-macroinitiator (mPEO-F) as starting material. The composition of the copolymer was obtained through NMR spectroscopy, whereas the molecular mass and degree of dispersity from light scattering and GPC/SEC. The CMC was obtained from the dependence of hydrodynamic radius (R) over the concentration and found that it was decreased with contents of polystyrene and temperature. The R dependence also indicated that shape of micelles change after certain concentration of copolymer. The reduced viscosity data plotted against concentration did not show a simple straight line as expected in case of polymers; rather, its slope was changed at a particular concentration, indicating sudden variation in the self-assembling behavior of the copolymers. The transmission electron microscopic (TEM) results of the material indicated the morphology pattern of two-dimensional arrays of hexagons with holes.