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@ARTICLE{Campanella:283343,
      author       = {Campanella, Antonella and Holderer, O. and Raftopoulos, K.
                      N. and Papadakis, C. M. and Staropoli, Mariapaola and
                      Appavou, M. S. and Müller-Buschbaum, P. and Frielinghaus,
                      H.},
      title        = {{M}ulti-stage freezing of {HEUR} polymer networks with
                      magnetite nanoparticles},
      journal      = {Soft matter},
      volume       = {12},
      number       = {13},
      issn         = {1744-6848},
      address      = {London},
      publisher    = {Royal Soc. of Chemistry},
      reportid     = {FZJ-2016-01771},
      pages        = {3214-3225},
      year         = {2016},
      abstract     = {We observe a change in the segmental dynamics of hydrogels
                      based on hydrophobically modified ethoxylated urethanes
                      (HEUR) when hydrophobic magnetite nanoparticles (MNPs) are
                      embedded in the hydrogels. The dynamics of the nanocomposite
                      hydrogels is investigated using dielectric relaxation
                      spectroscopy (DRS) and neutron spin echo (NSE) spectroscopy.
                      The magnetic nanoparticles within the hydrophobic domains of
                      the HEUR polymer network increase the size of these domains
                      and their distance. The size increase leads to a dilution of
                      the polymers close to the hydrophobic domain, allowing
                      higher mobility of the smallest polymer blobs close to the
                      “center”. This is reflected in the decrease of the
                      activation energy of the β-process detected in the DRS
                      data. The increase in distance leads to an increase of the
                      size of the largest hydrophilic polymer blobs. Therefore,
                      the segmental dynamics of the largest blobs is slowed down.
                      At short time scales, i.e. 10−9 s < τ < 10−3 s, the
                      suppression of the segmental dynamics is reflected in the
                      α-relaxation processes detected in the DRS data and in the
                      decrease of the relaxation rate Γ of the segmental motion
                      in the NSE data with increasing concentration of magnetic
                      nanoparticles. The stepwise (multi-stage) freezing of the
                      small blobs is only visible for the pure hydrogel at low
                      temperatures. On the other hand, the glass transition
                      temperature (Tg) decreases upon increasing the MNP loading,
                      indicating an acceleration of the segmental dynamics at long
                      time scales (τ ∼ 100 s). Therefore, it would be possible
                      to tune the Tg of the hydrogels by varying the MNP
                      concentration. The contribution of the static
                      inhomogeneities to the total scattering function Sst(q) is
                      extracted from the NSE data, revealing a more ordered gel
                      structure than the one giving rise to the total scattering
                      function S(q), with a relaxed correlation length ξNSE = (43
                      ± 5) Å which is larger than the fluctuating correlation
                      length from a static investigation ξSANS = (17.2 ± 0.3)
                      Å.},
      cin          = {JCNS (München) ; Jülich Centre for Neutron Science JCNS
                      (München) ; JCNS-FRM-II / Neutronenstreuung ; JCNS-1},
      ddc          = {530},
      cid          = {I:(DE-Juel1)JCNS-FRM-II-20110218 /
                      I:(DE-Juel1)JCNS-1-20110106},
      pnm          = {6215 - Soft Matter, Health and Life Sciences (POF3-621) /
                      6G15 - FRM II / MLZ (POF3-6G15) / 6G4 - Jülich Centre for
                      Neutron Research (JCNS) (POF3-623)},
      pid          = {G:(DE-HGF)POF3-6215 / G:(DE-HGF)POF3-6G15 /
                      G:(DE-HGF)POF3-6G4},
      experiment   = {EXP:(DE-MLZ)J-NSE-20140101 / EXP:(DE-MLZ)KWS1-20140101 /
                      EXP:(DE-MLZ)TEM-MLZ-20151210},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000372795100011},
      doi          = {10.1039/C6SM00074F},
      url          = {https://juser.fz-juelich.de/record/283343},
}