Effects of Poly(glycidyl ether) Structure and Ether Oxygen Placement on CO2 Solubility

The solubility of CO2 in poly(ethylene oxide), poly(ethyl glycidyl ether), poly(iso-propyl glycidyl ether), poly(allyl glycidyl ether), poly(n-butyl glycidyl ether), and poly(ethyl vinyl ether) was measured at room temperature and 333.15 K and pressures up to 15 bar. CO2 solubility, expressed as mole fraction in terms of molecular weight of the polymer repeat unit, was directly related to polymer repeat unit molecular weight regardless of pendant chain structure or ether oxygen placement in the backbone. The molality of CO2 was highest in poly(ethyl vinyl ether) and was equal in all the poly(glycidyl ethers) and poly(ethylene oxide). The standard enthalpies and entropies of CO2 absorption in poly(ethylene oxide), poly(ethyl glycidyl ether), and poly(ethyl vinyl ether) were calculated from the Henry's constants obtained from three isotherms. CO2 dissolution was slightly more favorable enthalpically in poly(ethylene oxide). However, the entropic penalty for absorption was lower in poly(ethyl glycidyl ether) and poly(ethyl vinyl ether). These results suggest that poly(glycidyl ethers) and poly(ethyl vinyl ether) are promising alternatives to poly(ethylene oxide) for CO2 separation by absorption or membrane separation because they have similar CO2, uptake capacity, low glass transition temperatures, are amorphous, and are more hydrophobic than poly(ethylene oxide).