(609c) Tunable Amphiphilic Pdmaema-b-PS Block Copolymer and Ionic Liquid Composite Thin Films for Gas Separations

Ionic liquid addition to polymer membranes has improved permselectivity in gas separations through enhanced gas transport. Supported ionic liquid membranes (SILMs) are the most facile method to incorporate ILs into polymer films, and SILMs offer improvement of permselectivity vs. permeability when compared to conventional polymer films. However, SILMs cannot perform gas separations at transmembrane pressures above 5 bar due to the extrusion of the capillary force supported IL. A biphasic thin-film using an amphiphilic block copolymer to encapsulate ionic liquid in the hydrophilic domain eliminates the risk of cross membrane pressures overpowering capillary forces. This study investigated the incorporation of two ionic liquids, [EMIM][TFSI] and [EMIM][SCN], within an amphiphilic biphasic block copolymer thin film comprised of tunable poly[2-(dimethylamino)ethyl methacrylate-b-styrene] (PDMAEMA-b-PS) blocks. Reversible addition-fragmentation chain transfer (RAFT) polymerization controlled block copolymer tunability, and the resulting polymers were characterized via gel permeation chromatography (GPC) and ¹H NMR. Thin films were cast using solvent-non-solvent induced phase separation (SNIPS) and characterized by fourier-transform infrared spectroscopy (FTIR), atomic force microscopy (AFM), and scanning electron microscopy (SEM). The casting solution composition was investigated to identify its influence on the homogeneity and properties of the resulting thin films. Results indicate that [EMIM][TFSI] was incompatible in the neat casting solution due to the precipitation of the polymer. In addition, the solvents DMSO and a mixture of DMF with THF did not properly dissolve both polymer and IL in the casting solution. However, the resulting neat films cast from solutions in pure DMF proved to be rigid and stable in formulations containing > 20 wt% of the block copolymer. Lag-time and continuous gas permeation experiments at 5, 10, and 15 bar were conducted on stable neat and IL-loaded thin films using CO₂ and CH₄.