Journal Article

FZJ-2020-05006

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Molecular Mobility of a Polymer of Intrinsic Microporosity Revealed by Quasielastic Neutron Scattering

Zorn, R.FZJ* ; Lohstroh, W. ; Zamponi, M.FZJ* ; Harrison, W. J. ; Budd, P. M. ; Böhning, M. ; Schönhals, A. (Corresponding author)

2020
Soc. Washington, DC

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Please use a persistent id in citations: http://hdl.handle.net/2128/26623  doi:10.1021/acs.macromol.0c00963

Abstract: 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) on microscopic timescales 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 threefold 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 energies for the methyl group rotation for PIM-1 and the polyimide are significantly higher than that for conventional polymers.

Keyword(s): Polymers, Soft Nano Particles and Proteins (1st) ; Soft Condensed Matter (2nd)

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Contributing Institute(s):

1. Neutronenstreuung (JCNS-1)
2. Neutronenstreuung und biologische Materie (IBI-8)
3. JCNS-FRM-II (JCNS-FRM-II)
4. JCNS-4 (JCNS-4)

Research Program(s):

1. 6G4 - Jülich Centre for Neutron Research (JCNS) (POF3-623) (POF3-623)
2. 551 - Functional Macromolecules and Complexes (POF3-551) (POF3-551)
3. 6215 - Soft Matter, Health and Life Sciences (POF3-621) (POF3-621)
4. 6G15 - FRM II / MLZ (POF3-6G15) (POF3-6G15)

Experiment(s):

1. SPHERES: Backscattering spectrometer (NL6S)
2. TOFTOF: Cold neutron time-of-flight spectrometer (NL2au)

Appears in the scientific report 2020

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Database coverage:
; ; Chemical Reactions ; Clarivate Analytics Master Journal List ; Current Contents - Physical, Chemical and Earth Sciences ; Ebsco Academic Search ; Essential Science Indicators ; IF >= 5 ; JCR ; Nationallizenz ; SCOPUS ; Science Citation Index Expanded ; Web of Science Core Collection

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