Hybrid effect of Ag ions and polarized Ag nanoparticles in poly(ethylene oxide)/AgBF₄/ionic liquid composites for long‐term stable membranes

Long‐term stability, high propylene/propane selectivity, and high mixed‐gas permeance have been required for the practical application of facilitated olefin transport membranes. In this study, we investigated poly(ethylene oxide) (PEO)/AgBF₄/1‐butyl‐3‐methylimidazolium tetrafluoroborate (BMIM⁺BF₄⁻) composite membranes to show high propylene/propane selectivity and permeance with long‐term stability. The PEO/AgBF₄/BMIM⁺BF₄⁻ composite membrane showed long‐term stability for more than 100 h with propylene/propane selectivity of 15, and mixed gas permeance of 12 GPU. These results were attributable to the sustainable carrier activity of Ag nanoparticles (NPs) stabilized by ionic liquid BMIM⁺BF₄⁻ when unstable Ag ions were converted into NPs during membrane operation for propylene/propane mixtures. Furthermore, an ionic liquid could plasticize the PEO chains to increase the chain flexibility, resulting in the high permeance despite of the formation of Ag NPs. The chemical and physical properties of the PEO/AgBF₄/BMIM⁺BF₄⁻ composite membrane were analyzed by SEM, TEM, FT‐IR, and TGA. POLYM. COMPOS., 40:2745–2750, 2019. © 2018 Society of Plastics Engineers