Pure- and mixed-gas transport properties of a microporous Tröger's Base polymer (PIM-EA-TB)

• Published in: Polymer (Guilford) 2021-11, Vol.236 (C), p.124295, Article 124295
• Main Authors: Park, Jaesung, Yoon, Hee Wook, Nassr, Mostafa, Hill, Matthew R., Paul, Donald R., Freeman, Benny D.
• Format: Article
• Language: English
• Subjects: Aging; Carbon dioxide; Fugacity; Gas permeation; Gas transport; Methane; Microporosity; Mixed-gas; Penetration; Permeability; Physical aging; PIM-EA-TB; Polymers; Pressure effects; Selectivity; Temperature; Transport properties
• ISSN: 0032-3861; 1873-2291
• DOI: 10.1016/j.polymer.2021.124295

Polymers of intrinsic microporosity (PIMs) offer tantalizing combinations of high selectivity and permeability in initial gas permeation measurements. Here, we report characterization of pure- and mixed-gas permeation properties of a thick (∼80 μm) PIM consisting of Tröger's Base (TB) and Ethanoanthracene (EA) films. The effects of feed pressure and temperature on pure-gas permeabilities of CH4, N2, O2, H2, and CO2 were investigated. The physical aging behavior of the thick film was tracked via pure-gas O2, N2, and CH4 permeability at 35 °C. Gas permeability decreased noticeably and selectivity increased as aging time increased. Particular attention was given to mixed-gas measurements of CO2 and CH4 (50/50) permeabilities at 35 °C and fugacities ranging from 2 to 18 atm to explore whether the rigid, bridged, bicyclic TB and EA units could resist CO2-induced plasticization. These results are presented along with pure-gas CO2 and CH4 results for membrane samples aged at different times. PIM-EA-TB aged for ∼24 h did not show signs of plasticization across the fugacity range considered. Dual-mode competitive sorption presumably caused the CO2/CH4 mixed-gas selectivity to be slightly higher than its corresponding pure-gas selectivity. However, as aging time increased, aged films underwent progressively more rapid and extensive CO2-induced plasticization with increasing fugacity, suggesting a systematic relationship between physical aging and plasticization in PIMs. Consequently, physical aging caused less improvement in mixed-gas CO2/CH4 selectivity than it did in pure-gas selectivity, due mainly to plasticization effects. [Display omitted] •Mixed-gas transport was characterized for CO2 and CH4 in PIM-EA-TB films.•A systematic relationship between physical aging and plasticization was observed.•As aging proceeded, PIMs became more susceptible to CO2-induced plasticization.