Polyimide-Ionene Hybrids: Accessing Vast Libraries of Novel Polymer Materials for Membrane Applications

Ionic liquids (ILs) in the forms of supported liquid membranes (SLMs) and polymerized ionic liquids (poly(ILs)) have been studied as media for gas separations for over a decade. Over that same time span, a number of other classes of polymer materials for gas separations including polyimides, thermally-rearranged (TR) polymers and polymers of intrinsic microporosity (PIMs) have also emerged. While ILs, poly(ILs), polyimides, TR-polymers and PIMs each possess distinct qualities, advantages and disadvantages, there has been little research that has sought to integrate the cationic charge associated with imidazolium rings directly into the backbone (rather than as pendants) of polyimides or other classes of polymer materials. There are a number of unique properties and behaviors that may arise from a precise spacing and alternating sequence of covalently tethered imide groups and imidazolium cations. Here, we present our design philosophy and progress in the development of polyimide-ionene hybrids and related materials as gas separation membranes.