Densities, Viscosities, and Self-Diffusion Coefficients of Several Polyethylene Glycols

Polyethylene glycol (PEG) is increasingly used as an alternative green chemical solvent. New experimental measurements on density, viscosity, and self-diffusion coefficient are presented for PEG200, PEG400, and several binary mixtures of tri- and hexaethylene glycol covering a temperature range from 298.15 to 358.15 K. Because PEGs are polydisperse, the exact compositions of PEG200 from six different vendors are analytically determined and found to be comparable. Thus, only two of the most differing PEG200 samples are further examined. The effects of water as the most common impurity on densities, viscosities, and self-diffusion coefficients are inspected as well as the results of the “dry” samples obtained by extrapolation to zero water content. The obtained results are carefully compared to the available literature data. The temperature dependence of these physical properties is investigated and found to be linear for density, while viscosity and self-diffusion coefficients follow the Arrhenius law. Attempts to calculate the properties of the binary mixtures and PEG200 samples from the mole fraction weighted average of the physical properties of the mixture components result in reasonable agreement. Agreement between calculated and measured molar volumes is within measurement uncertainty. Agreement of calculated and measured viscosities is mostly within a few percent but increases with decreasing temperature (largest viscosities) reaching values of up to 15%. Similarly, calculated and measured self-diffusion coefficients mostly agree within 20%, which is near the measurement uncertainty, but overestimates increase to 30% for the highest temperatures (largest self-diffusion coefficients).