M. Spitzer et al., Liquid biphase systems formed in ternary mixtures of two organic solvents and ethylene oxide oligomers or polymers, J BRAZ CHEM, 11(4), 2000, pp. 375-380
Phase equilibrium data were determined for ternary systems containing ethyl
ene oxide oligomers or polymers, heptane and one of three organic solvents
(methanol, dichloromethane or chloroform). The effects of temperature, of p
olymer molecular weight and of the chemical nature of the organic solvent o
n phase equilibrium were investigated. For all the studied systems, the mis
cibility region was reduced as temperature decreased, indicating an exother
mic phase separation process. For both binary and ternary mixtures, the mis
cibility also decreased as the macromolecule size increased, although this
effect was less significant for the ternary mixtures. These features sugges
t that phase separation is more influenced by enthalpic than entropic contr
ibutions. Regarding the different polar solvents investigated, methanol pre
sented a much smaller miscibility region, in accordance with its inferior s
olvation ability for PEO. The largest miscibility region was observed with
chloroform, not much different from the behaviour observed with dichloromet
hane. Tie lines were determined for some systems, confirming the strong seg
regation between polymer and the hydrocarbon solvent.