| Popis: |
Polymeric Ionic Liquids (PILs) are being considered as promising membrane materials for CO 2 separation. Present work aims at investigating effects substitution asymmetry on imidazole moiety of two structurally different polybenzimidazoles (PBI-BuI and PBI-HFA) on physical, gas sorption and transport properties of the resulting film forming PILs possessing symmetric substitution, while keeping one of the N - substituent as methyl group. PILs were obtained with high degree of substitution. The halide anion of these PILs was exchanged with BF 4 ¯, Tf 2 N¯ and HFB¯ anions. Effects of substituents, cationic backbone and type of anions on gas permeation properties of PILs using pure gases (He, H 2 , N 2 and CO 2 ) were examined at 20 atm upstream pressure and correlated with their physical properties. Combination of typical ionic liquid character (effective towards enhancing CO 2 sorption) and looser chain packing (ease in gas diffusion) offered improved CO 2 permeation characteristics. As an outcome, some of the PILs exhibited higher CO 2 permeation than that of hydrogen, typically known as ‘reverse selectivity’. These asymmetrically substituted PILs enhanced not only the gas permeability, but also selectivity than their symmetrically substituted counterparts. |
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