Incorporation of rigid polyaromatic groups in polybenzimidazole-based polymeric ionic liquids: Assertive effects on gas permeation properties

- Pyrenyl and anthryl group substituted PBI-based PILs were successfully synthesized.
- Excellent film forming nature of these PILs with varying anions is retained.
- Formed PILs showed higher CO2 permeability than earlier reported PBI based PILs.
- Higher CO2 based permselectivity in PILs than disubstituted analogue without IL functionality.
- Simultaneous tuning of gas diffusivity and solubility in glassy polymer was achieved.

Polymeric ionic liquids (PILs) have emerged as promising membrane materials for CO2 separation. The present work is aimed at investigating the effects of incorporation of rigid polyaromatic hydrocarbons, viz., pyrene and anthracene, in polybenzimidazole-based PILs. The effects of substituent and anion variation on the gas permeation properties of PILs using pure gases were examined at 20 atm upstream pressure. The results were correlated with physical properties of PILs. The pyrene substituted PIL exhibited ∼10 fold increase in CO2 permeability as compared to its precursor polymer PBI-BuI. The combination of a CO2 specific anion and bulky group substitution offered higher CO2 permeability as well as appreciable permselectivity than their structural analogue that was devoid of IL functionality. The permeation properties of present PILs were superior to those of conventional glassy polymers such as polysulfone, matrimid and polycarbonate which are widely studied for their gas permeation properties.

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