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.