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@ARTICLE{Zorn:888542,
      author       = {Zorn, Reiner and Lohstroh, Wiebke and Zamponi, Michaela and
                      Harrison, Wayne J. and Budd, Peter M. and Böhning, Martin
                      and Schönhals, Andreas},
      title        = {{M}olecular {M}obility of a {P}olymer of {I}ntrinsic
                      {M}icroporosity {R}evealed by {Q}uasielastic {N}eutron
                      {S}cattering},
      journal      = {Macromolecules},
      volume       = {53},
      number       = {15},
      issn         = {1520-5835},
      address      = {Washington, DC},
      publisher    = {Soc.},
      reportid     = {FZJ-2020-05006},
      pages        = {6731 - 6739},
      year         = {2020},
      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.},
      cin          = {JCNS-1 / IBI-8 / JCNS-FRM-II / JCNS-4},
      ddc          = {540},
      cid          = {I:(DE-Juel1)JCNS-1-20110106 / I:(DE-Juel1)IBI-8-20200312 /
                      I:(DE-Juel1)JCNS-FRM-II-20110218 /
                      I:(DE-Juel1)JCNS-4-20201012},
      pnm          = {6G4 - Jülich Centre for Neutron Research (JCNS) (POF3-623)
                      / 551 - Functional Macromolecules and Complexes (POF3-551) /
                      6215 - Soft Matter, Health and Life Sciences (POF3-621) /
                      6G15 - FRM II / MLZ (POF3-6G15)},
      pid          = {G:(DE-HGF)POF3-6G4 / G:(DE-HGF)POF3-551 /
                      G:(DE-HGF)POF3-6215 / G:(DE-HGF)POF3-6G15},
      experiment   = {EXP:(DE-MLZ)SPHERES-20140101 /
                      EXP:(DE-MLZ)TOF-TOF-20140101},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000562138100059},
      doi          = {10.1021/acs.macromol.0c00963},
      url          = {https://juser.fz-juelich.de/record/888542},
}