PIM-1 as an organic filler to enhance the gas separation performance of Ultem polyetherimide

An assortment of Ultem/PIM-1 polymer blends was prepared and their transport properties to a series of gases were studied. Good dispersion between the PIM-1 and Ultem phases was found when the PIM-1 loading was low (<20 wt%) or high (>90 wt%). A slight shift of Tg was observed when the PIM-1 loading increased from 0 wt% to 50 wt%, suggesting likely partially miscibility. The molecular-level interactions were further confirmed by the FTIR and XRD data, where shifts of peaks were detected at several compositions. Gas transport properties of pure gases including He, N2, O2, CH4, CO2 for all polymer blends and mixed gases including CO2/CH4 (50/50) and CO2/N2 (50/50) gas pairs for Ultem/PIM-1 (90:10) and Ultem/PIM-1 (80:20) blends were explored. Considerable increments in gas permeability were observed by adding only 5 or 10 wt% PIM-1 without much compromising gas pair selectivity, i.e., the CO2 permeability increased impressively over 47% and 167%, respectively, compared with the pristine Ultem. When comparing the gas permeation properties with the predictions from semi-logarithm and Maxwell equations, they follow nicely with the semi-logarithm addition when the PIM-1 loadings are low (<20 wt%), indicting relatively homogenous blends at these compositions, while the transport properties match closely with the Maxwell prediction at high PIM-1 loadings (>90 wt%) due to the good dispersion of Ultem inside PIM-1. This study opens up the potential of employing PIM-1 as an organic filler to improve the permeability of low permeable materials for other industrial membrane applications.