Cross-linked poly(ethylene oxide) (XLPEO) is one of the leading membrane materials for post-combustion CO2 capture because of its strong affinity toward CO2. For example, XLPEO prepared from poly(ethylene glycol) methyl ether acrylate (PEGMEA) exhibited CO2 permeability of 570 Barrer (1 Barrer = 10-10 cm3(STP) cm cm-2 s-1 cmHg-1) and CO2/N2 selectivity of 41 at 35oC. However, these XLPEOs cannot be dissolved in coating solutions, making them impossible to be fabricated into thin-film composite (TFC) membranes using state-of-the-art manufacturing processes. In this study, we synthesize high molecular weight yet soluble and amorphous aPEO via atom transfer radical polymerization (ATRP). The aPEO polymer exhibits CO2 permeability of 540 Barrer and CO2/N2 selectivity of 43. To make aPEO into TFC membrane, polydimethylsiloxane (PDMS) is chosen as the gutter layer between the porous support and selective layer and deposited with polydopamine (PDA) of &lt;10 nm. The PDA layer improves surface hydrophilicity and exerts affinity towards aPEO via hydrogen bonds, enabling the formation of defect-free aPEO as thin as 110 nm. The aPEO can also be blended with 18-crown-6 (C6) to further improve CO2 permeance because the addition of C6 increases the fractional free volume of the polymer. The effects of the PDA priming and C6 blending on the membrane performance are systematically investigated. For instance, introducing 40 mass% C6 in aPEO increases CO2 permeance from 1700 to 2200 GPU (1 GPU = 10-6 cm3(STP) cm-2 s-1 cmHg-1) and decreases CO2/N2 selectivity from 32 to 27 at 35oC. The membranes were also challenged with simulated flue gas containing water vapor and showed excellent stability, and the performance will be compared with the leading membranes reported for carbon capture.

Highly permeable thin-film composite membranes for CO2/N2 separation enabled by interfacial engineering

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