On the effect of polymer fractionation on phase equilibrium in CO₂ + poly(ethylene glycol)s systems

Phase equilibrium ratios of poly(ethylene glycol)s (PEG) of average molar masses 200, 400 and 600 with supercritical CO₂, were measured at 20 MPa and 313 K. Additional measurements with the monomer, ethylene glycol and with PEG 400 at 293 K were also performed. Three different methods of analysing the PEG amounts in each phase were used. Using a size exclusion chromatography procedure (SEC/GPC) we have observed a relevant fractionation of the polymer in the case of the system CO₂ + PEG 600. Some of the results obtained differ significantly from previously published values on the same systems. (C) 2000 Elsevier Science B.V.