Enhanced gas separation performance of PIM-1 blend membranes incorporating ionic liquid (3-(trimethoxysilyl) propan-1-aminium acetate ([APTMS][Ac])) as filler: Investigation of morphology, compatibility and transport properties

Blend membranes were fabricated by incorporating an ionic liquid, 3-(trimethoxysilyl) propan-1-aminium ace-tate ([APTMS][Ac]), as a filler into the polymer of intrinsic microporosity PIM-1. The analyses using FTIR spectroscopy, AFM, and SEM confirmed a uniform dispersion and excellent polymer-filler compatibility, even at higher loadings. Gas transport properties were assessed with filler loadings up to 10 wt% of IL, revealing a slight reduction in permeability but an enhancement in selectivity. CO2 permeability of the blend membrane decreased by 37% at 10% filler loading, while the ideal selectivity increased from 19.6 to 29.0 for CO2/CH4 and from 20.9 to 31.7 for CO2/N2 upon increasing [APTMS][Ac] content (0 wt% -10 wt%). The CO2/CH4 gas mixture selectivity rose by 58.62% and the CO2 permeability dropped by 40.44% compared to the pristine PIM-1 membrane. For the CO2/N2 gas mixture, the selectivity and CO2 permeability were enhanced by 40.11% and reduced by 39.07%, respectively. The permeability reduction can be ascribed to the filling of free volume voids in the PIM-1 polymer matrix by the IL [APTMS][Ac], while the selectivity improvement can be attributed to the strong interaction and high solubility of CO2 in the ionic liquid. The CO2 solubility coefficient increased with the rising IL concentration, indicating the high solubility of the IL in the polymer matrix.