Molecular engineering of PIM-1/Matrimid blend membranes for gas separation

The polymers of intrinsic microporosity have gained the attention as one of the potential materials for membrane gas separation. The contorted ladder-like structure in polymers of intrinsic microporosity, specifically PIM-1 possesses high permeability but with moderate selectivity for O ₂/N ₂, CO ₂/N ₂ and CO ₂/CH ₄ separation. We report here the most convenient and time efficient strategy of tuning the permeability and selectivity by blending PIM-1 with different compositions of Matrimid. In this work, the physical properties, phase behavior and gas transport properties of PIM-1/Matrimid blends have been explored. The polarized light microscope (PLM) analyses evidence that most of the PIM-1/Matrimid blends reveal partially miscible behavior. The inclusion of PIM-1 in the Matrimid matrix results in a substantial increase in gas permeability and a slight decrease in selectivity. The additions of 5 and 10wt% PIM-1 into Matrimid induce the permeability increments of 25% and 77%, respectively from the original 9.6 to 12 and 17Barrer without compromising its CO ₂/CH ₄ selectivity. For O ₂/N ₂ separation, the incorporation of a small amount of Matrimid (e.g., 5-30wt%) into PIM-1 promotes a fair increase in selectivity and drives the overall gas separation performance surpassing or close to the upper bound. At binary gas tests of CO ₂/CH ₄ (50%/50%), the 30wt% PIM-1 in Matrimid membrane has a CO ₂ permeability of 50Barrer and a CO ₂/CH ₄ selectivity of 31.