A coarsegrained model for symmetric ternary blends was constructed based on an experimental system of polyethylene/polyethylene oxide/polyethylenepoly(ethylene oxide)(PE/PEO/PEPEO) used in Batess work

and dissipative particle dynamics (DPD) method was employed to study the phase behavior of such ternary blends.Density distribution

order parameter and structure factor were used to characterize the phase and phase transition.The results show that the phase changes from lamellar (LAM) to bicontinuous microemulsion (BME) and then to macroscopic phase separation (PS) as the volume fraction of homopolymers H is increased.The phase sequences and their locations are in accordance with the experimental results.Especially

the BME region is located near the theoretical Lifshitz point.The LAM spacing increases with increasing H in LAM region and the interfacial tension decreases with increasing volume fraction of diblock copolymer (1-H) in PS region.Diblock copolymer molecules are disordered at interfaces due to the nature of curved interfaces in BME phase.The calculated structure factor on the BME structure is qualitatively in agreement with the TeubnerStrey static scattering model of microemulsion.In addition

the interfacial tension should reduce to a very low value in order to form stable BME structure.