Dual-strategy fabrication of thin-film Pebax membranes for CO2 separation: Hydrophilic gutter layer design and solvent-induced swelling

초록

Fabricating polyether block amide thin-film composite (TFC) membranes for CO2 separation remains challenging due to their high viscosity, microphase separation, and strong hydrophilicity. This study introduces a dual-strategy approach for the scalable fabrication of defect-free Pebax-1657 TFC membranes: (i) hydrophilic modification of the polydimethylsiloxane (PDMS) gutter layer via polyethylene glycol (PEG) through a two-step hydrosilylation, and (ii) solvent vapor-induced swelling of both the gutter and selective layers. PEG incorporation into PDMS and the resulting increase in hydrophilicity were confirmed by 1H NMR, XPS, and contact angle measurements, while swelling solvents were optimized through systematic analysis. The PEG-grafted PDMS (PDMS-PEG) gutter layer improves interfacial compatibility and coating uniformity. Swelling with hexane and ethanol vapor increases free volume and suppresses defect formation. This strategy enabled reproducible fabrication of large-area (14 x 10 cm2) Pebax-poly(poly(ethylene glycol) methyl ether acrylate) (Pebax-PPEG-MEA) membranes. The optimized membrane exhibited a CO2 permeance of 272 gas permeation units (GPU), with CO2/O2 and CO2/N2 selectivities of 14.0 and 32.0, respectively. Under mixed-gas conditions, the membrane maintained stable performance up to 20 atm, with long-term operational stability confirmed. This work demonstrates that integrating interfacial engineering with swelling control is critical for achieving high-performance gas separation membranes. The proposed approach offers a scalable and reproducible route for producing next-generation TFC membranes for energy-efficient CO2 capture applications.

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