Supercritical fluids have been used for the fractionation of poly(ethylene oxide). Indeed, supercritical fluids are well known for their efficiency in the fractionation of polymers. Polymer fractions of similar or lower molar mass distribution can be isolated with higher purity and lower energy costs than with other fractionation methods. The fractionation of poly(ethylene oxide) (POE) is reported at 423 K in the pressure range 8–35 MPa. Used as supercritical fluid HCFC 142b (1-chloro-1,1-difluoroethane, CH3CClF2) was found to be quite efficient, yielding polymers with a very narrow molar distribution. These results enable tochose the optimum pressure conditions for molecular architecture fractionation. The fractionation of a binary mixture of star and linear chains of poly(ethylene oxide) has been studied. The separation of linear chains and star structure appears to be very efficient for a short elution time