THE SOLUBILITY OF GASES IN AQUEOUS-SOLUTIONS OF POLYETHYLENE GLYCOLS

Measurements have been made to determine the solubilities of four gases, argon, methane, ethane, and propane, at 25°C in binary solutions of water with two commercially available polyethylene glycols (PEG), PEG 200 and PEG 400, over compositions ranging from 0 to 100% PEG. The two solutions exhibit a remarkable change in character at a composition of ∼70 wt% PEG which corresponds closely to a 1:1 mol ratio of water to ethylene oxide monomer. The gas solubilities determined for water-rich solutions are uniformly low and do not vary significantly from the respective solubilities in pure water, even at PEG concentrations in excess of 50 wt%. Above ∼70 wt% PEG, the solutions take on a distinctly different character in that the gas solubilities in these PEG-rich solutions are found to increase markedly with increasing PEG concentration. The degree of enhancement in gas solubility with added PEG follows the order C3H8 C2H6 CH4 Ar, with the result that the solubility data for each gas extrapolate smoothly into the respective solubilities in pure PEG. The solubility behavior of these solutions is not unlike that observed below and above the CMC of micellar solutions, and it is proposed that the enhanced sorptive capacity exhibited by these solutions at PEG concentrations in excess of 70 wt% reflects the presence of hydrophobic regions within the solution which result from weak association of incompletely hydrated PEG molecules. © 1991 Academic Press, Inc. All rights reserved.