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@ARTICLE{Zorn:903018,
      author       = {Zorn, Reiner and Szymoniak, Paulina and Kolmangadi, Mohamed
                      A. and Malpass-Evans, Richard and McKeown, Neil B. and
                      Tyagi, Madhusudan and Böhning, Martin and Schönhals,
                      Andreas},
      title        = {{L}ow {F}requency {V}ibrations and {D}iffusion in
                      {D}isordered {P}olymers {B}earing an {I}ntrinsic
                      {M}icroporosity as {R}evealed by {N}eutron {S}cattering},
      journal      = {Crystals},
      volume       = {11},
      number       = {12},
      issn         = {2073-4352},
      address      = {Basel},
      publisher    = {MDPI},
      reportid     = {FZJ-2021-04747},
      pages        = {1482 -},
      year         = {2021},
      abstract     = {The microscopic diffusion and the low frequency density of
                      states (VDOS) of PIM-EA-TB(CH3) are investigated by
                      inelastic and quasi-elastic neutron scattering where also
                      the demethylated counterpart of PIM-EA-TB(H2) is considered.
                      These intrinsic microporous polymers are characterized by
                      large BET surface area values of several hundred m2/g and
                      pore sizes between 0.5 and 2 nm. Detailed comparison is made
                      to the archetype of polymers of intrinsic microporosity,
                      PIM-1, and polynorbornenes also bearing a microporosity. Due
                      to the wavelength of neutrons, the diffusion and vibrations
                      can be addressed on microscopic length and time scales. From
                      the inelastic neutron scattering experiments the low
                      frequency density of states (VDOS) is estimated which shows
                      excess contributions to the Debye-type VDOS known as Boson
                      peak. It was found that the maximum frequency of the Boson
                      peak decreases with increasing microporosity characterized
                      by the BET surface area. However, besides the BET surface
                      area, additional factors such as the backbone stiffness
                      govern the maximum frequency of the Boson peak. Further the
                      mean squared displacement related to microscopic motions was
                      estimated from elastic fixed window scans. At temperatures
                      above 175 K, the mean squared displacement PIM-EA-TB(CH3) is
                      higher than that for the demethylated counterpart
                      PIM-EA-TB(H2). The additional contribution found for
                      PIM-EA-TB(CH3) is ascribed to the rotation of the methyl
                      group in this polymer because the only difference between
                      the two structures is that PIM-EA-TB(CH3) has methyl groups
                      where PIM-EA-TB(H2) has none. A detailed comparison of the
                      molecular dynamics is also made to that of PIM-1 and the
                      microporous polynorbornene PTCNSi1. The manuscript focuses
                      on the importance of vibrations and the localized molecular
                      mobility characterized by the microscopic diffusion on the
                      gas transport in polymeric separation membranes. In the
                      frame of the random gate model localized fluctuations can
                      open or close bottlenecks between pores to enable the
                      diffusion of gas molecules.},
      cin          = {JCNS-1 / IBI-8},
      ddc          = {540},
      cid          = {I:(DE-Juel1)JCNS-1-20110106 / I:(DE-Juel1)IBI-8-20200312},
      pnm          = {632 - Materials – Quantum, Complex and Functional
                      Materials (POF4-632) / 6G4 - Jülich Centre for Neutron
                      Research (JCNS) (FZJ) (POF4-6G4)},
      pid          = {G:(DE-HGF)POF4-632 / G:(DE-HGF)POF4-6G4},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000736984700001},
      doi          = {10.3390/cryst11121482},
      url          = {https://juser.fz-juelich.de/record/903018},
}