High-Pressure CO2 Sorption in Polymers of Intrinsic Microporosity under Ultrathin Film Confinement

Wojciech Ogieglo, Bader Ghanem, Xiaohua Ma, Matthias Wessling*, Ingo Pinnau

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

22 Scopus citations


Ultrathin microporous polymer films are pertinent to the development and further spread of nanotechnology with very promising potential applications in molecular separations, sensors, catalysis, or batteries. Here, we report high-pressure CO2 sorption in ultrathin films of several chemically different polymers of intrinsic microporosity (PIMs), including the prototypical PIM-1. Films with thicknesses down to 7 nm were studied using interference-enhanced in situ spectroscopic ellipsometry. It was found that all PIMs swell much more than non-microporous polystyrene and other high-performance glassy polymers reported previously. Furthermore, chemical modifications of the parent PIM-1 strongly affected the swelling magnitude. By investigating the behavior of relative refractive index, nrel, it was possible to study the interplay between micropores filling and matrix expansion. Remarkably, all studied PIMs showed a maximum in nrel at swelling of 2-2.5% indicating a threshold point above which the dissolution in the dense matrix started to dominate over sorption in the micropores. At pressures above 25 bar, all PIMs significantly plasticized in compressed CO2 and for the ones with the highest affinity to the penetrant, a liquidlike mixing typical for rubbery polymers was observed. Reduction of film thickness below 100 nm revealed pronounced nanoconfinement effects and resulted in a large swelling enhancement and a quick loss of the ultrarigid character. On the basis of the partial molar volumes of the dissolved CO2, the effective reduction of the Tg was estimated to be ∼200 °C going from 128 to 7 nm films.

Original languageEnglish (US)
Pages (from-to)11369-11376
Number of pages8
JournalACS Applied Materials and Interfaces
Issue number13
StatePublished - Apr 4 2018

Bibliographical note

Funding Information:
This publication is based on work supported by the King Abdullah University of Science and Technology (KAUST) Office of Sponsored Research (OSR) under Award No. SEED Fund OSR-2015-SEED-2445-01.

Publisher Copyright:
© 2018 American Chemical Society.


  • gas separations
  • gas sorption
  • high-pressure sorption
  • in situ ellipsometry
  • nanoconfinement
  • polymers of intrinsic microporosity

ASJC Scopus subject areas

  • Materials Science(all)


Dive into the research topics of 'High-Pressure CO2 Sorption in Polymers of Intrinsic Microporosity under Ultrathin Film Confinement'. Together they form a unique fingerprint.

Cite this