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@PHDTHESIS{Frenzel:429201,
      author       = {Frenzel, Lara},
      othercontributors = {Lehmkühler, Felix and Gruebel, Gerhard},
      title        = {{S}tructure and {D}ynamics of {C}omplex {L}iquids - {T}he
                      {P}hase {B}ehaviour of {S}ilica-{PNIPA}m {N}anogels},
      school       = {Universität Hamburg},
      type         = {Dissertation},
      address      = {Hamburg},
      publisher    = {Verlag Deutsches Elektronen-Synchrotron},
      reportid     = {PUBDB-2019-04870, DESY-THESIS-2019-032},
      series       = {DESY-THESIS},
      pages        = {101},
      year         = {2019},
      note         = {Dissertation, Universität Hamburg, 2019},
      abstract     = {In this thesis, the structure and dynamics of highly
                      concentrated core-shell nanogel particlescomposed of a
                      silica core and a poly(N-isoproylacrylamide) (PNIPAm) shell
                      suspendedin water are studied. The particles were
                      synthesised with dierent core-to-shell size ratiosand
                      prepared at various concentrations with volume fractions e
                      between approximately0:004 and 2. X-ray photon correlation
                      spectroscopy (XPCS) enables to follow the
                      dynamical,small-angle X-ray scattering (SAXS) the structural
                      changes of the thermo-responsivenanogel particles which
                      undergo a volume phase transition at a so-called lower
                      criticalsolution temperature (LCST) of 32C. All samples were
                      studied in a broad temperaturerange around the LCST with
                      approximately 15C < T < 45C and the main focus is
                      ondensely-packed systems.For a system with e = 0:55, the
                      structural relaxation time c was found to decreasewith
                      increasing temperature. Above the LCST, the structural
                      relaxation time initiallycontinues to decrease. The eect is
                      accompanied by a transition from stretched to
                      compressedexponential behaviour of the intensity
                      autocorrelation functions, which could bedetermined by
                      analysing the intensity autocorrelation functions. Upon
                      further heating asudden slowing down at a critical
                      temperature Tc 37C. In parallel, the q-dependenceof the
                      relaxation time shows an anomalous change from c / q􀀀3 to
                      c / q􀀀1. Theresults reveal a temperature-induced
                      transition from swollen repulsive particles with
                      polymerdriven dynamics at lower temperatures T < Tc towards
                      a colloidal gel composed ofcollapsed attractive particles.
                      The transition of structure and dynamics shows a
                      distinctdependency on the eective particle volume fraction.
                      Below a critical concentration notransition upon heating was
                      found.The de-swelling behaviour of the PNIPam nanogel was
                      inuenced with the additionof Trimethylamine N-oxide (TMAO)
                      to the concentrated particle suspension. With increasingTMAO
                      concentration, a shift of the LCST towards lower
                      temperatures and apreferential hydrophobic state could be
                      determined.With all results a full phase diagram of a
                      silica-PNIPAm core-shell system is presentedas a function of
                      temperature and concentration. It spans from dilute
                      suspensions toan eective volume fraction of more than ninety
                      percent covering two liquid phases, astructural
                      rearrangement phase and a colloidal gel phase.},
      cin          = {FS-CXS},
      cid          = {I:(DE-H253)FS-CXS-20130727},
      pnm          = {6215 - Soft Matter, Health and Life Sciences (POF3-621) /
                      6G3 - PETRA III (POF3-622)},
      pid          = {G:(DE-HGF)POF3-6215 / G:(DE-HGF)POF3-6G3},
      experiment   = {EXP:(DE-H253)P-P10-20150101 /
                      EXP:(DE-MLZ)External-20140101},
      typ          = {PUB:(DE-HGF)3 / PUB:(DE-HGF)29 / PUB:(DE-HGF)11},
      doi          = {10.3204/PUBDB-2019-04870},
      url          = {https://bib-pubdb1.desy.de/record/429201},
}