The Slightly Branched-Structure Design of Polyimides Simultaneously Enhances Anti-Plasticization and CO2 Separation Performance

The escalating demand for carbon capture has heightened interest in membrane-based gas separation technologies. Nevertheless, conventional polymeric membranes are constrained by plasticization and the trade-off between permeability and selectivity. In this study, we proposed a slightly branch-structure design strategy to construct branched polyimide (PI), which significantly enhances gas separation performance and anti-plasticization properties. With the incorporation of branched agent, the linear PI converts to branched PI, which suppresses chain dense packing and provides more free volume elements. Therefore, the branching architecture effectively restricts segmental mobility and reinforces interchain rigidity of PI, leading to significantly improved plasticization resistance from 16 atm to 30 atm. Interestingly, with the increase of rigid and free volume, the permeability and selectivity improved simultaneously in branched PI. Specifically, compared with pristine PI, the CO 2 permeability and CO 2 /CH 4 selectivity are increased by 139.7 % and 20 % in branched PI with 5wt% modification, respectively. Our findings proposed a simple and effective strategy for designing industrial polymers with improved performance and anti-plasticization properties for practical applications in gas separation membranes.