Synthesis and Gas Separation Performance of Poly(ionic liquid) Membranes Containing Branched and Cycloalkyl Group Functionalities

Abstract:   The use of poly ionic liquids (poly(ILs)) for CO₂ separation has been studied in the past decade as the need for solutions to CO₂ emissions has risen.  Alkyl-functionalized imidazolium-based poly(ILs) provide a tunable stage for gas separation.  The synthesis and characterization of branched and cycloalkyl functional groups on the imidazole ring are reported in this investigation.  Also reviewed, is the differences between straight-chain alkyl-functionalized imidazolium based poly(ILs) and their branched and cyclic equals.  In the counterparts of the straight-chained poly(ILs), a 20% increase in the selectivity of the membrane was observed for CO₂/N₂ and CO₂/CH₄.  However, a decrease in permeability of the cyclic and branched poly(IL) membranes is also seen.  This is plausibly due to the lower free volume in cyclic and branched functionalities as compared to those of the straight-chained imidazolium based poly(ILs).