Sorption, Dilation, and Partial Molar Volumes of Carbon Dioxide and Ethane in Cross-Linked Poly(ethylene oxide)

Experimental gas solubility and sorptive dilation data are reported for carbon dioxide and ethane in a cross-linked poly(ethylene oxide) rubber prepared by photopolymerization of poly(ethlyene glycol)diacrylate. Five different operating temperatures (253 <= T (K) <= 308) were considered, with a maximum gas pressure of 2.16 MPa (21.3 atm). The importance of taking sorptive dilation into account in the determination of gas solubility in polymers by the pressure-decay method was demonstrated. Sorption isotherms in terms of gas fugacity were described by the Flory-Huggins model. In the case of ethane, the Flory-Huggins interaction parameter was a decreasing function of temperature. In contrast, for carbon dioxide, a single parameter represented all isotherms. Dilation and sorption data were combined to calculate the partial molar volume (PMV) of the gases in the polymer, which was an increasing function of temperature. The PMV data were compared to the available literature data for other rubbery polymers and liquids. The chemical structure of the polymer influenced the PMV of the sorbed gas, and a correlation between matrix (i.e., solvent or polymer) solubility parameter and PMV was found.