Figure shows the change in mole % water for TBP and ( ) -( ), where the percentages have been normalized to the starting water content of the solvents. As the lengths of the PEGsubstituents increases, the mole % water also increases steadily. The increase in mole % water exceeds three orders of magnitude for (3). The amount of water measured by Karl Fisher titration after humidification was consistent for all three PEG-substituted solvents at 40 wt % after two weeks exposure. The tendency of etheric groups to increase the hydrophilic character of molecules has been documented by Menger and Chlebowski, who reported that etheric surfactants show less tendency to self-aggregate and are less likely to adsorb onto hydrophobic surfaces than similar surfactants lacking ether groups.[29] TBP, T i BP, and the PEG-substituted solvents prepared in this work were also tested for water absorption on the Hiden microbalance using humidified N2. Plots of moles of H2O absorbed per liter versus relative humidity are illustrated in Figure . TBP and T i BP were observed to absorb nearly identical amounts of water, taking up only 2 mol/L at 90% relative humidity. The PEG-substituted solvents were observed to take up nearly identical amounts of water under these conditions, at levels more than 4 times larger than TBP or T i BP. It is interesting that (1) -( ) show an exponential-type increase in water absorption with increasing humidity, while TBP and T i BP do not. Increasing numbers of etheric O atoms provide more water interaction sites in solvents ( ) -( ). Thus, both the CO2 and H2O absorption properties of these functionalized TBP analogues become less favorable upon inclusion of etheric groups.