Solvent activity measurements have been performed on the system poly(ethylene glycol) 400 (PEG 400) + methanol at T ) (298.15 to 328.15) K using the improved isopiestic method. The obtained solvent activity data were correlated with the original and modified Flory-Huggins models. It was found that for the studied system at any mass fraction, as the temperature is increased the solvent activity and Flory parameter are both decreased, indicating an increase of interaction between polymer and methanol as the temperature is increased. The density and speed of sound data were also measured at T ) (288.15 to 328.15) K for the PEG 400 + methanol system. From the obtained density values, the excess molar volume data were calculated and fitted to the Redlich-Kister equation. The excess molar isentropic compression values calculated from the measured speed of sound and density data were also fitted to the Redlich-Kister equation.

Solvent activity measurements have been performed on the system poly(ethylene glycol) 400 (PEG400) + ethanol at T ) (298.15 to 328.15) K using an improved isopiestic method. The solvent activity data were correlated with the original and modified Flory-Huggins models. The density, speed of sound, and viscosity data were also measured at T ) (288.15 to 328.15) K for the PEG400 + ethanol system. From these experimental data, the excess molar volume, V E , excess molar isentropic compression, K E s,m , and viscosity deviation, ∆η, have been determined for each composition and fitted to the Redlich-Kister equation.

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By using the improved isopiestic method, solvent activity measurements have been performed on the systems poly(ethylene glycol) 400 (PEG 400) + 1-propanol and 1-butanol at 298.15 K. Calcium chloride was used as the isopiestic standard for the calculation of activities. The obtained solvent activity data were correlated with the original Flory−Huggins model. The strength of interaction between different alcohols and the polymer was discussed on the basis of the obtained Flory−Huggins interaction parameters. Measurement of the density, speed of sound, and viscosity data were also performed at T = (288.15 to 328.15) K for the PEG 400 + 1-propanol and 1-butanol systems. The excess molar volume, V E , isentropic compression deviation, ΔK s , and viscosity deviation, Δη, have been calculated for each composition from the experimental data and fitted to the Redlich−Kister equation.

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