Previously, we investigated 1-n-alkylimidazoles as low viscosity, low vapor pressure physical solvents for CO2/CH4 separation and noted a decrease in performance as the length of the n-alkyl chain was extended. Here, we examine imidazoles featuring oligo(ethylene glycol) substituents ("PEG(n)-imidazoles") as an opportunity to improve upon the separation performance of this class of molecules. In the current work, we have characterized the density and the viscosity of PEG(n)-imidazoles over the temperature range 20-80 degrees C. PEG(n)-imidazoles are slightly more viscous than 1-n-alkylimidazoles but still fall below 20 cP. Ideal gas solubilities of CO2 and CH4 were measured in PEG(n)-imidazoles at gas partial pressures of similar to 5 bar and temperatures of 25-70 degrees C. Solubilities of CO2 and CH4 were both found to decrease with increasing temperature, with a stronger dependence for CO2. However, better CO2/CH4 selectivity was achieved in PEG(n)-imidazoles at lower operating temperatures than was observed for 1-n-alkylimidazoles. Physical properties and gas separation performances were correlated with fractional free volume calculated via COSMOtherm, as well as solubility parameters. The results show trends of decreased FFV when polar ether groups comprise the substituent, and that CO2 solubility and solubility selectivity for CO2/CH4 are improved compared to their nonpolar, hydrocarbon-based analogues.