Development of CO₂‐Philic Blended Membranes Using PIM–PI and PIM–PEG/PPG

Abstract Blending is a simple method through which one can effectively tailor new polymers exhibiting the properties of their parent ones. Because the original properties of polymers are maintained after blending, various studies have used these films as gas separation membranes. In this study, a new CO 2 separation membrane is developed by physically mixing a polymer of intrinsic microporosity (PIM) with high gas permeability, polyimide (PIM‐PI), as the hard segment and CO 2 ‐philic PIM‐poly(ethylene glycol)/poly(propylene glycol), or PIM‐PEG/PPG, as the soft segment. Prepared by adding 5 mol.% of PIM‐PEG/PPG to PIM‐PI, the blended membrane PPB‐5, with a tensile strength of 54 MPa and 35.5% elongation at break, shows better mechanical properties than commercial high‐performance polymer membranes developed for gas separation, PEG‐based blended membranes, and corresponding copolymer membranes with similar compositions developed in a previous study. In addition, it shows high CO 2 permeability (1552.6 Barrer) and CO 2 /N 2 selectivity (29.3) due to the well‐developed microphase separation characteristics originating from the optimal two‐component composition, and the gas separation performance is close to the Robeson (2008) upper bound.