Hybrid membranes of nanostructrual copolymer and ionic liquid for carbon dioxide capture

•Efficient CO2 capture membranes were prepared using hybrid of SBS-g-POEM and IL.•SBS-g-POEM was synthesized via mass-producible, low-cost radical polymerization.•IL was efficiently and uniformly distributed due to good miscibility and interactions.•SBS-g-POEM exhibited enhancement in CO2 permeability and selectivity.•SBS-g-POEM/IL15% hybrid showed the best performance due to unique nanostructure and morphology.

Efficient CO2 capture membranes were prepared using a hybrid comprising the poly(styrene-block-butadiene-block-styrene)-graft-poly(oxyethylene methacrylate) (SBS-g-POEM) nanostructural copolymer and the ionic liquid (IL) 1-ethyl-3-methylimidazolium dicyanamide (EMIMDCA). The SBS-g-POEM copolymer was synthesized via a mass-producible, cheap, free-radical polymerization process. The specific interaction of SBS-g-POEM with EMIMDCA and the good miscibility of these species were confirmed by Fourier transform infrared spectroscopy (FT-IR) and wide angle X-ray scattering (WAXS) and by using a universal testing machine (UTM). The microphase-separated nanostructure of the membranes and uniform distribution of EMIMDCA were also observed using transmission electron microscopy (TEM) and small angle X-ray scattering (SAXS). The neat SBS membrane exhibited a CO2 permeability of 372 Barrer (1 Barrer = 10−10 cm3(STP)·cm/(cm2·s·cmHg) and CO2/N2 selectivity of 16.4; these values increased to 407 Barrer and 21.6, respectively, for the SBS-g-POEM membrane due to the high CO2 affinity of the polar POEM side chains. Upon incorporation of EMIMDCA, the CO2 permeability increased to 514 Barrer without a large sacrifice of the selectivity. In contrast, the blend of neat SBS and EMIMDCA did not show any gas separation ability due to the inhomogeneity and poor mechanical properties, indicating the importance of grafting POEM to the SBS main chains.

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