Semi-interpenetrating polymer network membranes based on a self-crosslinkable comb copolymer for CO₂ capture

High-performance, semi-interpenetrating polymer network (semi-IPN) membranes are prepared by incorporating a self-crosslinkable comb copolymer into the matrix of Pebax, a commercially available block copolymer with rigid polyamide blocks and soft polyethylene oxide blocks. The comb copolymer, poly(glycidyl methacrylate-g-polypropylene glycol)-co-poly(oxyethylene methacrylate) (PGP-POEM) is synthesized via one-pot free-radical polymerization and undergoes epoxide-amine self-crosslinking reaction without any additional catalyst or thermal treatment. The structural, thermal, and mechanical properties as well as the gas-separation performance of the membrane are systematically investigated by varying the content of PGP-POEM in the Pebax matrix. As the PGP-POEM loading is increased, the CO₂ permeability gradually increases without significant loss of CO₂/N₂ selectivity. The self-crosslinked PGP-POEM comb copolymer not only effectively degrades the crystalline structure of Pebax by disturbing the chain-packing but also provides numerous CO₂-philic groups, resulting in both increased diffusivity and solubility of CO₂. As compared to neat Pebax membrane, the semi-IPN membrane containing 40 wt% PGP-POEM exhibits approximately 2.5-fold enhancement in CO₂ permeability (up to 236.6 Barrer) with similar CO₂/N₂ selectivity (38.8) as that of neat Pebax membrane. This work suggests that the semi-IPN membrane based on a self-crosslinkable comb copolymer has great promise for application in CO₂ capture owing to its high performance and simple preparation process.