Elevating gas separation performance of Pebax-based membranes by blending with a PDMS-PEO block copolymer for CO2 capture and separation

Polymeric membranes have become an emerging technology for gas separation applications. High-performance and low-cost polymeric membranes are desirable for various industrial applications. Polymer blending is a simple and versatile method to improve the separation performance of membranes. In the present work, we have significantly improved the gas separation performance of the poly(ether-block-amide) (Pebax-1657) membrane by blending it with polydimethylsiloxane-polyethylene oxide (PDMS-PEO) block copolymers. The optimal Pebax-1657/PDMS-PEO blend membrane consists of 80 wt% of PDMS-PEO (Mn = 600 g/mol, ∼60 wt% of PEO content). In pure gas tests, it can elevate the CO₂ permeability of the neat Pebax-1657 membrane by about 13 folds (1300 %) from 119 to 1629 Barrer, while the ideal CO₂/N₂ selectivity only decreases by around 25 % from 42 to 32. Interestingly, the corresponding ideal CO₂/H₂ and CO₂/CH₄ selectivities increase slightly to ∼10. The remarkable enhancements in gas separation performance arise from the strong increases in the solubility of polar gas CO₂ and solubility selectivity of CO₂/non-polar light gas (e.g. N₂) as well as a noticeable improvement in CO₂ diffusivity as the PDMS-PEO loading increases. The impressive improvements in gas separation performance coupled with the commercially available and affordable raw materials (Pebax-1657 and PDMS-PEO) render the Pebax-1657/PDMS-PEO blend membrane promising and attractive to the industrial deployments and applications for CO₂ capture and separation.