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@PHDTHESIS{Vakili:422891,
      author       = {Vakili, Mohammad},
      othercontributors = {Trebbin, Martin and Pearson, Arwen},
      title        = {{M}icrofluidic {S}ample {E}nvironments for {T}ime-resolved
                      {M}acromolecular {S}tructure {F}ormation {S}tudies},
      school       = {University of Hamburg},
      type         = {Dissertation},
      address      = {Hamburg},
      reportid     = {PUBDB-2019-02383},
      pages        = {186},
      year         = {2019},
      note         = {Dissertation, University of Hamburg, 2019},
      abstract     = {This thesis deals with the polymerization-induced
                      self-assembly (PISA) of amphiphilic blockcopolymer
                      nano-objects, which were synthesized using a controlled
                      radical polymerization(CRP) method, in particular, the
                      reversible addition-fragmentation chain-transfer
                      (RAFT)aqueous polymerization in the presence of a
                      poly(N,N-dimethylacrylamide) stabilizer agent(macro RAFT
                      agent). Besides the use of N-isopropylacrylamide (NIPAm) as
                      core-formingblock for thermo-responsive nanoparticle, the
                      aqueous dispersion polymerization of 2-methoxyethyl acrylate
                      (MEA) was pursued as a model to study
                      hydrophilic-hydrophobic phasetransitions: as a monomer, MEA
                      is water-soluble. However, upon chain growth, the
                      poly(MEA)block becomes hydrophobic which eventually drives
                      micellar self-assembly. The underlyingprocesses and the time
                      scales of the self-assembly are still not completely
                      understood.Finding the answers to such questions can be
                      answered by the investigation of a system’s
                      timeresolvedreaction kinetics and structural dynamics in
                      situ. However, it can be challenging tocontrol the
                      experimental conditions accurately, such as the precise
                      initiation of a reaction byrapid mixing. This challenge can
                      be overcome by using microfluidic reaction systems
                      whichenable precise control over fluids within micron-sized
                      channels. These very well defined flowand reaction
                      conditions make microfluidics predestined for the
                      time-resolved studies ofpolymers using X-ray sources. In
                      microfluidic laminar flows, the temporal structural
                      evolutionduring a polymerization process can be mapped onto
                      different positions in the downstreammicrochannel. Besides
                      the ability to access time scales down to the
                      microseconds-scale, thisapproach has many advantages
                      compared to more traditional set-ups in terms of a low
                      sampleconsumption (experiments on the nanoliter scale),
                      highly efficient and homogeneous mixing bydiffusion, as well
                      as the possibility to adjust the temporal resolution by
                      manipulation of the flowrates.Microfluidic channels can be
                      fabricated using a number of different materials, each
                      havingdifferent optical and mechanical properties as well as
                      manufacturing challenges: glass, metaland most importantly
                      polymers, such as polydimethylsiloxane (PDMS), thermoplastic
                      cyclicolefin copolymers (TOPAS® COC) or highly inert
                      polyimide films (Kapton®) are currentlyused. With the
                      advent of more powerful and brighter X-ray sources, COCs and
                      Kapton inparticular have received tremendous interest as
                      sample environment due to their X-raycompatibility and low
                      background signal. Another approach for low-background
                      sampleenvironments are microfluidic liquid jet devices based
                      on the gas dynamic virtual nozzle(GDVN) design. These
                      devices contain a network of very narrow channels and
                      nozzles andprovide a very defined free-flowing sample stream
                      in vacuum, making them especiallydesirable for experiments
                      at X-ray free electron laser (XFEL) facilities.In this work,
                      the tailored design, fabrication and experimental
                      implementation of novelmicrofluidic sample environments that
                      address specific experimental conditions for
                      controlledradical polymerization are described. In
                      particular, these devices were applied to in situ
                      timeresolveddiffusive mixing experiments to access very
                      early stages of the PISA reaction. In situhere means
                      monitoring the structural changes during chain growth/phase
                      transition by probingthe sample with X-rays while the
                      polymerization/self-assembly occurs.Supported by
                      complimentary dynamic light scattering (DLS) experiments,
                      fluorescentmicroscopy and 3D finite-element computational
                      fluid dynamics (CFD) simulations, theinsights of these
                      experiments aim to provide a better understanding of
                      amphiphilic blockcopolymer self-assembly and, in general,
                      may help to tailor polymers for their specificapplications,
                      such as micellar drug delivery vehicles in medical
                      applications.},
      cin          = {UNI/CUI / UNI/PHY / UNI/INF},
      cid          = {$I:(DE-H253)UNI_CUI-20121230$ /
                      $I:(DE-H253)UNI_PHY-20170505$ /
                      $I:(DE-H253)UNI_INF-20151211$},
      pnm          = {6G3 - PETRA III (POF3-622) / DFG project 194651731 - EXC
                      1074: Hamburger Zentrum für ultraschnelle Beobachtung
                      (CUI): Struktur, Dynamik und Kontrolle von Materie auf
                      atomarer Skala (194651731) / PHGS, VH-GS-500 - PIER
                      Helmholtz Graduate School $(2015_IFV-VH-GS-500)$},
      pid          = {G:(DE-HGF)POF3-6G3 / G:(GEPRIS)194651731 /
                      $G:(DE-HGF)2015_IFV-VH-GS-500$},
      experiment   = {EXP:(DE-H253)P-P03-20150101 /
                      EXP:(DE-H253)CFEL-Exp-20150101 /
                      EXP:(DE-MLZ)External-20140101},
      typ          = {PUB:(DE-HGF)11},
      doi          = {10.3204/PUBDB-2019-02383},
      url          = {https://bib-pubdb1.desy.de/record/422891},
}