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@PHDTHESIS{Zhang:1007082,
      author       = {Zhang, Chunchen},
      othercontributors = {Möller, Martin and Pich, Andrij},
      title        = {{R}eversible gelation, thermoresponsiveness and formation
                      of double networks by {N}-alkylated poly({N}-vinylamide)s},
      school       = {RWTH Aachen University},
      type         = {Dissertation},
      address      = {Aachen},
      publisher    = {RWTH Aachen University},
      reportid     = {RWTH-2025-02930},
      pages        = {1 Online-Ressource : Illustrationen},
      year         = {2025},
      note         = {Veröffentlicht auf dem Publikationsserver der RWTH Aachen
                      University; Dissertation, RWTH Aachen University, 2025},
      abstract     = {Poly(N-vinylamide)s are attractive building blocks for
                      hydrogels due to their good biocompatibility and versatile
                      substitution at the amide position or after hydrolysis via
                      the amine function. Gels of poly(N-alkyl-N-vinylamides) with
                      short N-alkyl side chains exhibit a volume phase transition
                      in water, similar to which is observed for
                      poly(N-isopropylacrylamide). This has been rarely
                      investigated so far. In this work, firstly,
                      poly(N-alkyl-N-vinylamide)s with different alkyl chain
                      length (n) and degree of substitution (DS) were prepared by
                      N-alkylation of poly(N-vinylamide)s. Inverse molecular
                      weight dependence of the cloud points of
                      poly(N-alkyl-N-vinylamide)s (n = 3 or 4) polymers were
                      observed meaning that the lower molecular weight samples
                      have lower cloud points. Next, three types of hydrogels were
                      prepared from the aforementioned polymers: (i) reversibly
                      crosslinked hydrogels prepared from
                      poly(N-alkyl-N-vinylamide)s (n = 10 to 18, DS = 3 $mol\%);$
                      (ii) covalently crosslinked thermoresponsive hydrogels
                      prepared from sparsely allylated poly(N-alkyl-N-vinylamide)s
                      (n = 3 or 4) crosslinked by photo-initiated crosslinking via
                      thiol-ene reaction; (iii) thermoresponsive double network
                      hydrogels prepared from the combination of polymers used for
                      Type (i) and Type (ii) hydrogels. Swelling,
                      thermoresponsiveness and rheological properties of the
                      aforementioned hydrogels were investigated. The strain- and
                      stress-controlled rheological experiments of Type (i)
                      hydrogels demonstrated no crystalline ordering even in the
                      case of longer side chains, the network will be connected by
                      amorphous and thus liquid hydrophobic clusters, i.e., the
                      side chains are sticky attachments to the hydrophilic
                      polymer backbone, whose stickiness is systematically
                      increased by their length. Furthermore, their rheological
                      properties follow a time-temperature-stickiness
                      superposition principle indicating that the side chains
                      serve as sticky substituents which extend the terminal
                      relaxation time according to their hydrophobicity.
                      Furthermore, these hydrogels demonstrated low cytotoxicity.
                      Type (ii) hydrogels were characterized for their
                      temperature-dependent swelling and swelling kinetics. It was
                      observed that once the hydrogels collapsed at elevated
                      temperature, swelling would recover below the volume phase
                      transition temperature in short time but only to reduced
                      degree of swelling. Further swelling to the original degree
                      of swelling appeared to be extremely slow and was difficult
                      to be observed because of the long times needed. For each
                      network of Type (iii) hydrogels, polymers with different
                      alkyl chain lengths and molecular weights were employed to
                      study the effects on the temperature-dependent swelling
                      behavior and mechanical properties of the double network
                      hydrogels. Enhanced mechanical strength and tissue-like
                      stress-strain mechanical response were achieved for selected
                      double network hydrogels.},
      cin          = {154610 / 150000 / 052200},
      ddc          = {540},
      cid          = {$I:(DE-82)154610_20140620$ / $I:(DE-82)150000_20140620$ /
                      $I:(DE-82)052200_20140620$},
      typ          = {PUB:(DE-HGF)11},
      doi          = {10.18154/RWTH-2025-02930},
      url          = {https://publications.rwth-aachen.de/record/1007082},
}