Interactions of polyethylene glycols with water studied by measurements of density and sound velocity

Densities and sound velocities of ethylene glycol (EG) and polyethylene glycols (PEGs) of molecular weight 200, 300, 400, 550, 600, 1000, 1450, 3350, 8000, and 10,000 at (288.15, 298.15, and 308.15) K were measured with high precision vibrating tube densimeter and sound velocity measuring device. They were used to evaluate apparent molar volumes, V∅, and apparent molar isentropic compressibilities, KΦS. Infinite dilution values of these parameters, V∅∘, and KΦS∘, were obtained from their plot as a function of molality. The variations of V∅∘, and KΦS∘, with the number of repeating units in PEGs and with temperature were examined. Comparison of the experimentally obtained data was made with the available literature data and also with some values predicted according to group additivity approach. The results were interpreted in terms of hydration and conformational effects of PEGs in water. A correlation was also examined between V∅∘ or KΦS∘ values of PEGs in water and equilibrium moisture contents of PEGs as well as the water vapor permeabilities (WVP) of edible films containing PEGs.