REPRESENTATION OF VAPOR LIQUID AND LIQUID LIQUID EQUILIBRIA FOR BINARY-SYSTEMS CONTAINING POLYMERS - APPLICABILITY OF AN EXTENDED FLORY HUGGINS EQUATION

For some binary systems, an extended Flory-Huggins equation is applicable to both vapor-liquid equilibria (VLE) and liquid-liquid equilibria (LLE) using the same adjustable parameters. New LLE and VLE data are reported for polystyrene (PS) (MW = 100,00)/cyclohexane and for poly(ethylene glycol) (PEG) (MW = 8,000)/water. Experimental results for the PS/cyclohexane system agree well with the semiempirical model, whereas those for PEG/water do not, probably because, for PEG/water, the temperature range of the VLE data is about 55-degrees-C lower than that of the LLE data. Excellent fits were obtained for our previously published experimental results for PS/cyclohexane (upper critical solution temperature, UCST), PS/ethyl acetate (lower critical solution temperature, LCST), PS/tert-butylacetate and PS/methyl acetate (both UCST and LCST), and PEG/water (closed-loop). The semiempirical model also fits well with new data obtained for the polymer blend PS/poly(vinyl methyl ether).