Fabrication of Thin Ion-Gel Membrane by Interfacial Polymerization

In this study, we propose interfacial polymerization as a suitable methodology for the fabrication of thin-gel membranes containing ionic liquids (ILs). Tetra-armed poly(ethylene glycol) (tetra-PEG) is a key material that forms a gel network via click reactions between tetra-PEG prepolymers with different terminal functional groups. At the interface between the aqueous and IL phases, thiol-terminated tetra-PEG and maleimide-terminated tetra-PEG react to form a single-micrometer-thick ion gel layer with a tetra-PEG network. The thickness of the ion-gel layer could be controlled by varying the reaction time and concentration of the prepolymers. The IL content of the ion-gel layer was approximately 80 wt %. A thin-film composite (TFC) membrane with a thin ion-gel layer was fabricated, and its CO₂ separation performance was evaluated. The CO₂/N₂ selectivity of approximately 28 indicated that the thin ion-gel layer was defect-free. Because of the high IL content of the thin ion-gel layer, the TFC membrane exhibited a high CO₂ permeability of 726 barrer. Interfacial polymerization is an effective method for preparing thin, defect-free, high-IL content ion-gel membranes.