Molecular simulation of poly(VDF-HFP) copolymer with imidazolium-based ionic liquid as an effective medium for biogas separation

Abstract

The embedding of ionic liquids (ILs) into the polymer membrane matrix affects the morphology and properties of the material. Due to the unique nature of ILs, including high thermal stability and the ability to selectively absorb various gases, polymer-IL systems generally exhibit improved separation properties. In this work, the CO2/CH4 separation properties of poly (vinylidene fluoride-co-hexafluoropropylene)) (poly (VDF-HFP)) with different amounts of 1-ethyl-3-methylimidazolium bis (trifluoromethylsulfonyl) imide ([EMIM] [TFSI]) were simulated by classical molecular dynamics (MD). MD simulations were per-formed using the GROMACS program with an AMBER force field for various polymer chain lengths (8, 10 and 12 mer) and different IL concentrations (0, 20, 40, 60 and 80 wt%) in the polymer. While the increased affinity of CO2 for the membrane containing a high concentration of IL was observed, the effect of IL on the affinity of CH4 was found to be negligible. A benefit of understanding the mechanism of gas absorption in polymeric-IL systems and revealing the interactions of gas molecules with IL and polymer molecules at the molecular level indicates the potential of MD simulation for understanding processes in membrane gas separations.