Novel Ionic Liquid/Polyetherimide Composite Membranes: The Interplay of Transport Properties and Membrane Structure

Abstract

Novel composite membranes based on high-performance poly(ether imide sulfone) (XH-1015, EXTEM™ RESIN) were developed by incorporating 20–60 wt.% of hydrophobic protic ionic liquid, 2-butylaminoimidazolinium bis(trifluoromethylsulfonyl)imide ([BAIm][TFSI]). Structure-properties relationships for the membrane were investigated by using EDS, FTIR, DSC, TGA, and sessile-drop water contact angle measurements. The interaction between the carbonyl group of the imide cycle and imidazolinium cations via hydrogen bonding was evident. The introduction of 20–60 wt.% [BAIm][TFSI] at PEI matrix significantly reduces the glass transition temperature by 84–216°C, respectively, and enhances the surface's hydrophilicity. All the membranes revealed excellent thermal stability up to 400°C. The membranes were tested for their gas permeability as potential gas sensors for CO2 or membrane materials. The unusual transitions of gas permeability mechanism with increasing [BAIm][TFSI] content in the composite were discovered opening a possibility to fabricate a functionally hierarchical membrane for tunable separation of gases from complex mixtures.