Amidoxime-functionalized tetraphenylethylene ladder polymer for efficient membrane-based gas separations

Yingge Wang, Vikas Kumar, Fawwaz Elahi, Bader Ghanem, Marcel Balcik, Jie Shen, Yu Han, Ingo Pinnau*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

2 Scopus citations


Recent advances in solution-processible polymers of intrinsic microporosity (PIM) have attracted extensive research efforts in membrane-based gas separations due to their significantly enhanced gas permeability originating from inefficient chain packing. However, PIM-based membrane materials exhibit typically only moderate gas-pair selectivity, which is often insufficient especially for challenging gas separations containing highly sorbing feed components such as CO2. More importantly, they suffer from CO2-induced polymer chain dilation commonly referred as plasticization, which leads to poor separation performance under aggressive CO2/CH4 mixed-gas testing conditions. In this work, we conducted amidoxime (AO)-functionalization on a microporous tetraphenylethylene-based ladder polymer (TPE-PIM) by reacting its nitrile groups with hydroxyl amine under reflux conditions. Because of strong inter-chain hydrogen bonding, AO-functionalized TPE polymer (AO-TPE) exhibited a tightened and rigidified microstructure with 64 % reduction in Brunauer-Emmett-Teller (BET) surface area (175 m2/g) as compared to TPE-PIM (485 m2/g) derived from N2 adsorption isotherms at 77 K. As a result, fresh AO-TPE showed decreased gas permeability concurrent with a two-fold increase in CO2/CH4 selectivity (from 18 to 40) compared to TPE-PIM. Under aggressive 50:50 CO2:CH4 mixed-gas testing conditions, AO-TPE showed a strong plasticization resistance with decreased CH4 permeability over total feed pressure ranging from 4 to 30 bar. At 20 bar total pressure, AO-TPE demonstrated a mixed-gas CO2/CH4 selectivity of 37.7 as compared to 14.5 for TPE-PIM. The simple AO functionalization strategy holds promise to be an effective post-modification method to increase gas selectivity and alleviate the detrimental effects from CO2-induced plasticization.

Original languageEnglish (US)
Article number112896
JournalEuropean Polymer Journal
StatePublished - Apr 15 2024

Bibliographical note

Publisher Copyright:
© 2024 Elsevier Ltd


  • Amidoxime-functionalization
  • CO/CH mixed-gas separation
  • Hydrogen bonding
  • Plasticization resistance
  • Polymers of intrinsic microporosity
  • Tetraphenylethylene

ASJC Scopus subject areas

  • General Physics and Astronomy
  • Polymers and Plastics
  • Organic Chemistry
  • Materials Chemistry


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