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@ARTICLE{Friedrich:10528,
      author       = {Friedrich, T. and Tieke, B. and Meyer, M. and
                      Pyckhout-Hintzen, W. and Pipich, V.},
      title        = {{T}hermoresponsive copolymer hydrogels based on
                      n-isopropylacrylamide and cationic surfactant monomers
                      prepared from micellar solution and microemulsion in a
                      one-step reaction},
      journal      = {The journal of physical chemistry / B},
      volume       = {114},
      issn         = {1520-6106},
      address      = {Washington, DC},
      publisher    = {Soc.},
      reportid     = {PreJuSER-10528},
      pages        = {5666 - 5677},
      year         = {2010},
      note         = {This research project has been supported by the European
                      Commission under the seventh Framework Programme through the
                      Key Action: Strengthening the European Research Area,
                      Research Infrastructures. Contract No.: 226507 (NMI3). The
                      DFG is thanked for financial support (project TI 219/10-1
                      and 10-2, priority program 1256 "Intelligent hydrogels").
                      Prof. Dr. K. Meerholz is thanked for providing the scanning
                      electron microscope and Ruth Broker for taking the SEM
                      images.},
      abstract     = {Thermoresponsive hydrogels were prepared upon
                      radiation-induced copolymerization of aqueous micellar
                      solutions containing N-isopropylacrylamide (NiPAAm) and a
                      cationic surfactant monomer (surfmer), and of microemulsions
                      containing NiPAAm, surfmer, and styrene. Three surfmer
                      compounds were used:
                      (11-(acryloyloxy)undecyl)trimethylammonium bromide (AUTMAB),
                      (11-(methacryloyloxy)undecyl)trimethylammonium bromide
                      (MUTMAB), and
                      (2-(methacryloyloxy)ethyl)dodecyldimethylammonium bromide
                      (MEDDAB). Comonomer solutions were studied on their phase
                      behavior and structure using small-angle neutron scattering
                      (SANS). The presence of surfmers increased the solubility of
                      NiPAAm in the aqueous phase. SANS studies indicate that the
                      surfmers form spherical micelles, which in the presence of
                      styrene are increased and in the presence of NiPAAm are
                      decreased in size. Styrene is incorporated in the core, and
                      NiPAAm is incorporated in the shell of the micelles. If
                      styrene and NiPAAm are present, the effects of both
                      compensate each other, the micelle size remains unchanged,
                      and only small amounts of styrene are solubilized.
                      Evaluation of scattering curves indicated remarkable changes
                      in headgroup dissociation of surfmers in the presence of
                      NiPAAm in the micellar solutions. If exposed to (60)Co-gamma
                      irradiation (dose: 80 kGy), stable, transparent, and
                      thermoresponsive hydrogels were directly obtained. The lower
                      critical solution temperature (LCST) of gels containing
                      surfmer in low concentration was higher than that for pure
                      NiPAAm gels, whereas in gels with high surfmer concentration
                      it was lower. The lowest LCST was observed if MEDDAB was
                      present in the gel. 1 $\%$ (w/w) was already sufficient to
                      lower the LCST from 33.2 to 28.5 degrees C. Gels with low
                      surfmer concentration (< or = 1 wt $\%)$ exhibited a strong,
                      rapid swelling in water at 20 degrees C and a rapid and
                      reversible shrinking at 50 degrees C. For a gel containing
                      $1\%$ AUTMAB, the swelling ratio was 2.4 times higher
                      (MUTMAB, 2.8; MEDDAB, 1.5) than that for a pure NiPAAm gel.
                      Copolymer gels containing more than 1 wt $\%$ surfmer
                      exhibited a strong and rapid swelling below and above the
                      LCST, because the copolymerized ionic surfmer induced an
                      osmotic pressure in the gel. The effects of a variation of
                      NiPAAm and surfmer concentration were studied, and the
                      origins of the thermoresponsive properties are discussed.},
      keywords     = {J (WoSType)},
      cin          = {IFF-5 / IFF-4 / Jülich Centre for Neutron Science JCNS
                      (JCNS) ; JCNS},
      ddc          = {530},
      cid          = {I:(DE-Juel1)VDB785 / I:(DE-Juel1)VDB784 /
                      I:(DE-Juel1)JCNS-20121112},
      pnm          = {BioSoft: Makromolekulare Systeme und biologische
                      Informationsverarbeitung / Großgeräte für die Forschung
                      mit Photonen, Neutronen und Ionen (PNI) / NMI3 - Integrated
                      Infrastructure Initiative for Neutron Scattering and Muon
                      Spectroscopy (226507)},
      pid          = {G:(DE-Juel1)FUEK505 / G:(DE-Juel1)FUEK415 /
                      G:(EU-Grant)226507},
      experiment   = {EXP:(DE-MLZ)KWS2-20140101},
      shelfmark    = {Chemistry, Physical},
      typ          = {PUB:(DE-HGF)16},
      pubmed       = {pmid:20394351},
      UT           = {WOS:000277053900004},
      doi          = {10.1021/jp911358z},
      url          = {https://juser.fz-juelich.de/record/10528},
}