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@PHDTHESIS{Bochenek:819253,
      author       = {Bochenek, Steffen},
      othercontributors = {Richtering, Walter and Isa, Lucio},
      title        = {{M}icrogels at liquid interfaces},
      school       = {RWTH Aachen University},
      type         = {Dissertation},
      address      = {Aachen},
      publisher    = {RWTH Aachen University},
      reportid     = {RWTH-2021-04937},
      pages        = {1 Online-Ressource : Illustrationen, Diagramme},
      year         = {2021},
      note         = {Veröffentlicht auf dem Publikationsserver der RWTH Aachen
                      University 2021; Dissertation, RWTH Aachen University, 2020},
      abstract     = {Microgels are three-dimensional, cross-linked polymer
                      networks of colloidal size which are dispersed in and
                      swollen by a good solvent. They combine properties of
                      polymers and colloidal particles, such as their swelling or
                      deswelling in response to external stimuli or their
                      crystallization at higher volume fractions. Furthermore,
                      microgels have been shown to readily adsorb to interfaces
                      and form responsive or ``smart'' emulsions, foams and
                      coatings. Though having an isotropic, spherical shape in
                      bulk solution, the microgels become anisotropic upon
                      adsorption. The structure of regular cross-linked microgels
                      at interfaces is described by a core-corona morphology. In
                      this thesis, the temperature-sensitivity and
                      polymer-to-particle transition of microgels at fluid
                      interfaces are investigated. The two-dimensional phase
                      diagram of poly(N-isopropylacrylamide) (pNIPAM) microgels
                      below and above their volume phase transition temperature is
                      investigated with a combination of compression isotherms,
                      atomic force microscopy, image analysis, and reflectometry
                      methods. At low compression, the interaction between
                      adsorbed microgels is dominated by their highly stretched
                      corona and the phase behavior of the microgel monolayers is
                      the same. The polymer segments within the interface lose
                      their temperature-sensitivity due to the influence of
                      surface free energy. At high compression, however, the
                      portions of the microgels that are located in the aqueous
                      side of the interface become relevant and prevail in the
                      microgel interactions. These portions are able to deswell
                      and, consequently, the isostructural phase transition is
                      altered. It is shown that this effect is presented at both
                      decane- and air-water interface. Thus, the
                      temperature-dependent swelling perpendicular to the
                      interface (``3D'') affects the compressibility parallel to
                      the interface (``2D''). Different pNIPAM-based systems,
                      starting from linear polymers, through regular cross-linked,
                      to hollow microgels were investigated. Similar to microgels
                      in bulk solution, it is shown that the deformability and
                      softness of microgels, due to the constraints of the polymer
                      network, is a dominant property for the interfacial
                      behavior. Their soft interaction potential cannot only be
                      tuned by the variation of cross-linker but also by the
                      architecture of the polymeric network, e.g., the
                      incorporation of a solvent filled cavity. A closer look was
                      taken at the polymer-to-particle transition. Therefore,
                      ultra-low cross-linked (ULC) microgels were investigated,
                      which are the pNIPAM microgels with the lowest number of
                      cross-linking points within their network that can be
                      synthesized by precipitation polymerization. Their phase
                      behavior and rheological properties in bulk are those of
                      soft colloids. However, when these microgels are confined at
                      an oil-water interface, their compression isotherms resemble
                      that of flexible polymers and a concentration-dependent
                      topography is observed. Depending on the compression, these
                      microgels can behave as flexible polymers, covering the
                      substrate with a uniform film, or as colloidal microgels
                      leading to a monolayer of particles.},
      cin          = {153310 / 150000},
      ddc          = {540},
      cid          = {$I:(DE-82)153310_20140620$ / $I:(DE-82)150000_20140620$},
      pnm          = {SFB 985 B08 - Mikrogele an fluiden Grenzflächen (B08)
                      (317425935) / DFG project 191948804 - SFB 985: Funktionelle
                      Mikrogele und Mikrogelsysteme (191948804)},
      pid          = {G:(GEPRIS)317425935 / G:(GEPRIS)191948804},
      typ          = {PUB:(DE-HGF)11},
      doi          = {10.18154/RWTH-2021-04937},
      url          = {https://publications.rwth-aachen.de/record/819253},
}