Improving CO2 permeability in polymerized room-temperature ionic liquid gas separation membranes through the formation of a solid composite with a room-temperature ionic liquid

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 RTILs and polymers. Incorporation of just 20 mol% free RTIL in the polymer membrane yields a stable composite material with a CO2 permeability increase of similar to 400% with a 33% improvement to CO2/N-2 selectivity relative to the analogous poly(RTIL) membrane lacking any free ion pairs. The composite membrane also showed a significant improvement in CO2/CH4 separation compared to other poly(RTILs) when analyzed via "Robeson Plots." This new approach to polymer gas separation membranes provides a powerful method to improve the performance of current materials without intensive organic synthesis. Copyright (C) 2008 John Wiley & Sons, Ltd.