PHASE-BEHAVIOR OF AQUEOUS POLY(ETHYLENE OXIDE) POLY(PROPYLENE OXIDE) SOLUTIONS

The phase behavior of aqueous solutions of poly(ethylene oxide) (PEO) and poly(propylene oxide) (PPO) has been investigated. Experimentally, it was observed that the ternary phase diagram displays a closed immi scibility region. At 25-degrees-C, the tie lines indicate that each ph ase is enriched in one of the polymers. Furthermore, the water content is higher in the PEO-enriched phase. Increasing the temperature, i.e. , worsening the solvency for both PPO and PEO, results in a growth of the immiscibility region. Furthermore, the relative water content in t he PPO-enriched phase decreases, whereas PEO distributes more evenly b etween the phases. A good agreement was found between the experimental findings and results from model calculations using a mean-field theor y for polymers possessing internal states. Furthermore, details about the state distributions of PEO and PPO are discussed.