Nanostructures and CO₂/gas separation characteristics of polymerized anionic liquids containing perfluoroalkyl sulfonylimide

Polymerized anionic liquids (a-PILs) with anions covalently bonded to hydrocarbon polymer chains and free cations have recently emerged as an interesting materials platform for designing CO₂ separation membranes. Herein, we report a series of a-PILs containing anions with short perfluorinated alkyl chains from 1-ethyl-3-methylimidazolium ([C₂mim]) 3-acryloxypropylsulfonyl(-x-[sulfonimide]) (where x represents the perfluoroalkyl carbon length). The PEAx is further plasticized by ionic liquids (ILs) of [C₂mim] bis(-y-[sulfonylimide]) (EMy, where y is the perfluoroalkyl carbon length). The effects of perfluoroalkyl carbon lengths and EMy loading on polymer structures and CO₂/gas separation properties are systematically investigated. Adding EMy dramatically increases CO₂ permeability and CO₂/gas selectivity, which can be explained using the Vogel–Fulcher–Tammann (VFT) equation. This study illustrates the unique gas separation characteristics derived from fluorinated a-PILs with delocalized anionic charges, and understanding their structure and property relationship can be used to guide the design of the next-generation (polymerized) ionic liquids for membrane applications.