Gas solubility, diffusivity and permeability in poly(ethylene oxide)

The effect of pressure on the solubility, diffusivity, and permeability of He, H₂, O₂, N₂, CO₂, CH₄, C₂H₄, C₂H₆, C₃H ₆ and C₃H₈ in poly(ethylene oxide) (PEO) is reported at 35°C. 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°C and infinite dilution, semi-crystalline PEO exhibits CO₂ permeability coefficient of 12 Barrers, and CO ₂/H₂ and CO₂/N₂ 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 CO ₂/N₂ 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°C. At similar conditions, PE exhibits propylene-propane selectivity of only 1.4.