Polymers of Intrinsic Microporosity Having Bulky Substitutes and Cross-Linking for Gas Separation Membranes
Xiuling Chen, Zhiguang Zhang, Lei Wu, Xingchen Liu, Shan Xu, Johnson E. Efome, Xinghua Zhang, Nanwen Li
Abstract
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).