The effect of pressure on the solubility, diffusivity, and permeability of He, H-2, O-2, N-2, CO2, CH4, C2H4, C2H6, C3H6 and C3H8 in poly(ethylene oxide) (PEO) is reported at 35 degreesC. Additionally, the temperature dependence of permeability is reported. The effect of polar ether linkages in PEO on gas transport is illustrated by comparing transport properties in PEO with those in polyethylene (PE). For example, at 35 degreesC and infinite dilution, semi-crystal line PEO exhibits CO2 permeability coefficient of 12 Barrers, and CO2/H-2 and CO2/N-2 pure gas selectivities of 6.7 and 48, respectively. In contrast, at similar conditions, the permeability of PE to CO2 is 13 Barrers, but the CO2/N-2 selectivity is only 13. In addition to good separation properties for quadrupolar-nonpolar gas pairs, PEO also shows interestingly high selectivity for olefins over paraffins, which is ascribed to favorable interaction between the polar ether groups in PEO and olefins. For example, the infinite dilution permeability of PEO to propylene is 3.8 Barrers and pure gas propylene-propane selectivity is 2.7 at 35 degreesC. At similar conditions, PE exhibits propylene-propane selectivity of only 1.4. (C) 2004 Elsevier B.V. All rights reserved.