Effect of structure of poly(ionic liquids)-based membrane on gas transport

Gas separation based on polymeric materials has been well established due to low cost. However, there is a trade-off between selectivity and permeability which impede its practical application. Among promising materials, poly(ionic liquids) (PolyILs) composed of anion and cation ions in the system shows good mechanical stability, easy processability, and higher CO₂ absorption.
The mobility of either cation or anion in PolyILs can affect its gas transport because the gas transport properties can be controlled by changing chemistry and flexibility of the polymer chains which lead to the control over free volume. We, therefore, prepare two sets of PolyILs through RAFT polymerization to understand the structural effect of PolyILs for gas transport. Both synthesized PolyILs have the same chemical configuration composed of imidazolium and (trifluoromethane)sulfonamide component, but mobile ion is different for each system.
We found that imidazolium-based PolyILs with (trifluoromethane)sulfonamide as mobile ion have higher CO₂ and helium gas permeability compared to the other PolyILs configuration, resulting in higher selectivity of CO₂/N₂ and He/N₂. Mechanical studies were performed to understand gas transport. We also incorporated MOFs particle to improve CO₂ permeability.