Wettability improvement of polydimethylsiloxane to enhance interfacial compatibility in multilayer composite membranes with implications for gas separation

Polydimethylsiloxane (PDMS)-based composite membranes are widely utilized in gas separation. However, their inherent hydrophobicity leads to interfacial defects when combined with hydrophilic layers, limiting performance improvement. Herein, we first use electrospun polyimide fibers as support layers, combine them with PDMS, and adopt a synergistic strategy involving amphiphilic molecular interlayering of surfactant Tween 20 and in situ growth of ZIF-67 to regulate interfacial properties and microstructure, thereby enhancing H 2 /CO 2 separation performance. The modified PDMS exhibits significantly enhanced wettability, with the contact angle decreasing from 138° to 0° and maintaining good stability. This improvement arises from the enrichment between hydrophilic hydroxyl groups of Tween 20 on the surface and the entanglement of its hydrophobic alkyl chains with PDMS segments. Additionally, Tween 20 bridges the intermediate layer and the separation layer via hydrogen bonds, eliminates interlayer voids, and increases tensile strength from 33.75 to 47.49 MPa, thus optimizing interfacial compatibility. The dual distribution of ZIF-67 in both the support and separation layers, combined with interfacial optimization, constructs an integrated adsorption-diffusion-sieving transport pathway. The composite membrane achieves a H 2 permeability of 109.5 Barrer and a H 2 /CO 2 selectivity of 6.5, which are 23.9 % and 30.0 % higher than those of unmodified membranes, respectively. Molecular simulations clarify the structure-performance relationship between wettability, interfacial strength, and gas transport. This synergistic strategy demonstrates potential applications in membrane engineering, providing valuable references for designing high-performance polymer/MOF composite membranes and expanding their use in multi-system gas separations.