A new segment-level mixing strategy to improve the gas separation performances of carbon molecular sieve membrane derived from polymer blends

A novel mixing strategy for optimizing the structures and gas separation properties of carbon molecular sieve membranes (CMSMs) through the precise segment-level mixing of polyimide-co-siloxane (PSI) blends is proposed. PSI copolymers with different contents of siloxane were synthesized and blended, denoted as PSI-0, PSI-1, PSI-2, and PSI-3 based on the molar ratio of DABA:siloxane, 10:0, 9:1, 8:2, and 7:3, respectively. This study focuses on unraveling the intricate interplay between repeating segment distribution and resulting carbonization structures, with a specific emphasis on the gas separation performances of CMSMs. Of particular interest is the PSI-0:PSI-3 (1:2) blend, which, despite containing an identical siloxane amount to neat PSI-2, yields a CMSM with comparable hydrogen permeability and significantly enhanced selectivity (232 % H2/CH4 and 184 % H2/N2 selectivity). These findings underscore the critical role of segment distribution in achieving superior gas separation performances, presenting a promising avenue for the precise engineering of polymer precursor structures to optimize CMSM properties.