Copolymer SAFT modeling of phase behavior in hydrocarbon-chain solutions: Alkane oligomers, polyethylene, poly(ethylene-co-olefin-1), polystyrene, and poly(ethylene-co-styrene)

The copolymer SAFT equation of state is found to represent phase transitions in the normal-alkane and methyl-alkane solutions in methane, ethane, propane, and n-hexane, the polyethylene and poly(ethylene-co-olefin-1) solutions in propane, and the polystyrene solutions in n-butane. The pure-solute parameters are all estimated on the basis of the molecular weight and structure only, and the one temperature-independent and system-independent (within each class of solutes) binary parameter is set equal to a constant. The segment energy of the methyl branches is found to be around 160 K, which is lower than the corresponding backbone energy, while the segment energy of the benzene branches is found to be around 222 K for polystyrene, which is higher than the corresponding backbone energy. The alkyl branches are found to promote the polymer miscibility while the benzene branches are found to inhibit the polymer miscibility in propane.