Solid, polymer membranes fabricated from room-temperature ionic liquid monomers
containing oligo (ethylene glycol) or nitrile-terminated alkyl substituents tethered to
imidazolium cations were found to exhibit ideal CO2/N2 and CO2/CH4 separation factors
significantly greater than those with comparable length n-alkyl substituents, with similar CO2
permeability. Polymers containing these functional groups exhibited CO2/N2 gas separation
performance exceeding the “upper bound” of a “Robeson Plot”.

Room‐temperature ionic liquids (RTILs) present a number of unique opportunities for the
processing and tailoring of polymer materials for applications including ion conduction
polymers, catalysis, and gas separations. Perhaps most importantly, RTILs can be
synthesized as monomers and polymerized in the presence of non‐polymerizable RTILs to
provide solid composites with enhanced properties. These features allow for the formation of
poly (RTIL)–RTIL composite gas separation membranes, exhibiting hybrid properties of both …