Cloud-point measurements for salt + poly(ethylene glycol) + water systems by viscometry and laser beam scattering methods

The phase separation of salt + poly(ethylene glycol) + water systems was studied by cloud‐point measurements using viscometry and laser beam scattering methods. The Flory–Huggins model was applied to determinate the condition for salt‐induced liquid–liquid phase separation in the system. A temperature‐ and concentration‐dependent interaction parameter was employed to fit the phase diagrams for the systems. The temperature and concentration functionality of the interaction parameter was determined and used to predict cloud‐point curves for the systems. The cloud‐point curves were found to be in quantitative agreement with experimental data. Also, the effect of various salts on the measured cloud points was studied. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1983–1990, 2003