Molecular mobility of a polymer of intrinsic microporosity revealed by quasielastic neutron scattering

  • Quasielastic neutron scattering by employing a combination of time-of-flight and backscattering techniques is carried out to explore the molecular mobility of a polymer of intrinsic microporosity (PIM-1) at microscopic time scales in comparison with a high-performance polyimide. Molecular fluctuations can change the structure of the temporary network of micropores and open or close pathways for gas molecules. Therefore, the investigation might help to understand the selectivity of PIMs in gas separation processes. The performed neutron scattering experiments provide evidence for a low-temperature relaxation process, which was assigned to methyl group rotation. This methyl group rotation was analyzed in terms of jump diffusion in a three-fold potential. The analysis results in a fraction of methyl groups which are immobilized. For PIM-1 it was found that the fraction of immobilized methyl groups decreases with increasing temperature up to 350 K. At higher temperatures the number ofQuasielastic neutron scattering by employing a combination of time-of-flight and backscattering techniques is carried out to explore the molecular mobility of a polymer of intrinsic microporosity (PIM-1) at microscopic time scales in comparison with a high-performance polyimide. Molecular fluctuations can change the structure of the temporary network of micropores and open or close pathways for gas molecules. Therefore, the investigation might help to understand the selectivity of PIMs in gas separation processes. The performed neutron scattering experiments provide evidence for a low-temperature relaxation process, which was assigned to methyl group rotation. This methyl group rotation was analyzed in terms of jump diffusion in a three-fold potential. The analysis results in a fraction of methyl groups which are immobilized. For PIM-1 it was found that the fraction of immobilized methyl groups decreases with increasing temperature up to 350 K. At higher temperatures the number of immobilized methyl group increases gain due to an underlying relaxation process. This motional process on a somewhat larger length scale might lead to a reversible structural rearrangement which partially hinders the strongly localized methyl group rotation. In addition, it was found that the activation energy for the methyl group rotation for PIM-1 and the polyimide is significantly higher than for conventional polymers.zeige mehrzeige weniger

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Metadaten
Autor*innen:R. Zorn, W. Lohstroh, M. Zamponi, W. Harrison, P. Budd, Martin BöhningORCiD, Andreas SchönhalsORCiD
Dokumenttyp:Zeitschriftenartikel
Veröffentlichungsform:Verlagsliteratur
Sprache:Englisch
Titel des übergeordneten Werkes (Englisch):Macromolecules
Jahr der Erstveröffentlichung:2020
Organisationseinheit der BAM:6 Materialchemie
6 Materialchemie / 6.6 Physik und chemische Analytik der Polymere
7 Bauwerkssicherheit
7 Bauwerkssicherheit / 7.5 Technische Eigenschaften von Polymerwerkstoffen
Verlag:American Chemical Society
Verlagsort:Washington, DC
Jahrgang/Band:53
Ausgabe/Heft:15
Erste Seite:6731
Letzte Seite:6739
Freie Schlagwörter:Polymer of intrinsic microporosity; Quasielastic neutron scattering
Themenfelder/Aktivitätsfelder der BAM:Chemie und Prozesstechnik
Material
DOI:10.1021/acs.macromol.0c00963
ISSN:0024-9297
ISSN:1520-5835
Verfügbarkeit des Dokuments:Datei im Netzwerk der BAM verfügbar ("Closed Access")
Datum der Freischaltung:02.09.2020
Referierte Publikation:Ja
Datum der Eintragung als referierte Publikation:10.09.2020
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