VOLUMETRIC PROPERTIES OF DILUTE AQUEOUS-SOLUTIONS OF POLY(ETHYLENE GLYCOLS)

In the reported experiments, the densities of aqueous solutions of some poly(ethylene glycols) (mono-, di-, tri-, and tetraethylene glycol, and four carbowaxes with a mean molecular weight ranging from 600 to 15,000), and of di-, tri-, and tetraethylene glycol dimethyl ether have been determined at 25 degree C, in the concentration range 5-100 g/liter. From these data, the limiting partial specific and/or molar volume of the solute has been calculated. A value of 37. 0 ml/monomole has been evaluated for the partial molar volume of the repeating unit-CH//2CH//2O-, and has been found independent of both terminal groups and chain length. The results suggest that the ethylene units in higher polymers are accessible to the solvent as easily as in oligomers, and support an ″open″ or extended conformation of the poly(ethylene glycol) chain in aqueous dilute solution. This interpretation has been confirmed by a comparison of the experimental values of partial molar volume with the values calculated by semiempirical models.