Polymers of Intrinsic Microporosity Having Bulky Substitutes and Cross-Linking for Gas Separation Membranes

Certain polymers with very high free volume demonstrate a continuous network of interconnected void spaces due to the shape and rigidity of its macromolecular composition; as such, it becomes an intrinsic property for these polymers otherwise seen as polymers of intrinsic microporosity (PIM). Methylated polymers of intrinsic microporosity (PIM-M), bromoalkylated PIM (PIM-BM-x), and thermally self-cross-linked PIM-BM-x were designed and prepared for gas separation performance enhancements. The PIM-BM-x polymeric membranes demonstrated exceptional gas separation performance compared with PIM-M and surpassed the 2008 Robeson upper bound line, that is, the selectivities of PIM-BM-100 membrane for CO2/CH4 and O2/N2 were as high as 25.8 and 5.6, respectively. The gas permeability testing indicated that the permeability of CO2 and O2 for the cross-linked PIM-BM-70 was 48.3 and 11.1 barrer, respectively, while the selectivities of CO2/CH4 and O2/N2 were, respectively, 43.9 and 6.5 after self-cross-linking at 300 °C for 5 h. More importantly, the cross-linked membrane showed excellent antiplasticization ability with a plasticization pressure higher than 500 psi. This value is relatively greater than the pristine uncross-linked PIM-BM membrane (100 psi).