New Poly(ionic liquid) - Ionic Liquid - Zeolite Mixed-Matrix Membranes Made with Curable Poly(ionic liquid) Oligomers of Controlled Length for CO2/CH4 Separations

We report new mixed-matrix membranes (MMMs) for CO₂/light gas separations that are formed by combining zeolite particles, ionic liquids (ILs), and curable poly(IL)s and cross-linking the latter in situ around the other two ionic components. Controlled radical polymerization was used to tune the length of the curable poly(IL) component, allowing control over initial reactive mixture viscosity and final MMM mechanical properties. The resulting cured MMMs have CO₂ permeabilities of 43 barrers with CO₂/CH₄ selectivities of ca. 30. These curable poly(IL) – IL – zeolite mixtures can be solvent-cast, unlike earlier small-molecule IL monomer-based MMM-forming systems, allowing these new MMMs to be processed into thin films. We demonstrate that the chain length of the curable poly(IL) oligomers impacts the CO₂/light gas selectivity and permeability of these MMMs, with longer curable poly(IL) chains leading to higher separation performances.