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@ARTICLE{Lund:18197,
      author       = {Lund, R. and Willner, L. and Pipich, V. and Grillo, I. and
                      Lindner, P. and Colmenero, J. and Richter, D.},
      title        = {{E}quilibrium {C}hain {E}xchange {K}inetics of {D}iblock
                      {C}opolymer {M}icelles: {E}ffect of {M}orphology
                      {M}acromolecules},
      journal      = {Macromolecules},
      volume       = {44},
      issn         = {0024-9297},
      address      = {Washington, DC},
      publisher    = {Soc.},
      reportid     = {PreJuSER-18197},
      pages        = {6145 - 6154},
      year         = {2011},
      note         = {The authors acknowledge support of the European Community
                      within the Soft Comp Network of Excellence (NoE) program.
                      R.L. and J.C. also acknowledge support from the following
                      grants: GIC07/35-IT-463-07, MAT2007-63681, and
                      CSD2006-00053.},
      abstract     = {In this work, we present the chain exchange kinetics in
                      block copolymer micelles of spherical and cylindrical
                      geometry. The aim of this work was to understand the
                      mechanisms controlling the molecular exchange with a
                      particular focus to delineate any potential effect of the
                      micellar morphology. As model system symmetric short-chain
                      amphiphilic poly(ethylene-alt-propylene)-poly(ethylene
                      oxide) diblock copolymer (PEP1-PEO1, numbers denote
                      approximate molecular weight in l(D) in aqueous solutions
                      has been used. This system undergoes a irreversible cylinder
                      to sphere transition upon addition of N,N-dimethylformamide
                      (DMF) as cosolvent or upon heating. This feature allowed to
                      quantitatively compare chain exchange kinetics in both
                      morphologies. The kinetics were accessed by using
                      hydrogen/deuterium labeling and time-resolved small-angle
                      neutron scattering experiments employing a stopped flow
                      apparatus by which the kinetics could be followed from about
                      some hundreds of milliseconds up to hours. The results show
                      that, independent of morphology, all data can be
                      satisfactorily described by a scaling model that takes into
                      account the polydispersity of the core forming PEP block in
                      order to describe the broad logarithmic time decay at longer
                      times. A small but significant effect of the morphology
                      could be seen which was reflected in a slightly accelerated
                      kinetics for spherical micelles. A detailed comparison shows
                      that for both morphologies, the activation energy follows a
                      scaling law proportional to the product of the interfacial
                      tension, gamma, and the number of repeat units of the,
                      insoluble block, N-B, i.e., E-a similar to gamma N-B rather
                      than the gamma N-B(2/3) predicted by Halperin and Alexander.
                      This implies a stretched conformation of the insoluble block
                      during the expulsion process compared to the more globular
                      shape considered in the original scaling theory. This can be
                      related to insufficient chain length/statistics for these
                      rather small chains to form a globule during the expulsion
                      process; or to an higher polymer density within the corona
                      of these "crew cut" type micelles. Through the analysis, the
                      faster kinetics could be summarized in a slightly smaller
                      activation energy for the spherical micelles which is
                      probably related to small changes in the internal corona
                      structure.},
      keywords     = {J (WoSType)},
      cin          = {ICS-1 / JCNS (München) ; Jülich Centre for Neutron
                      Science JCNS (München) ; JCNS-FRM-II / JCNS-1 / JCNS-2},
      ddc          = {540},
      cid          = {I:(DE-Juel1)ICS-1-20110106 /
                      I:(DE-Juel1)JCNS-FRM-II-20110218 /
                      I:(DE-Juel1)JCNS-1-20110106 / I:(DE-Juel1)JCNS-2-20110106},
      pnm          = {BioSoft: Makromolekulare Systeme und biologische
                      Informationsverarbeitung / Großgeräte für die Forschung
                      mit Photonen, Neutronen und Ionen (PNI)},
      pid          = {G:(DE-Juel1)FUEK505 / G:(DE-Juel1)FUEK415},
      experiment   = {EXP:(DE-MLZ)KWS2-20140101},
      shelfmark    = {Polymer Science},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000293353800041},
      doi          = {10.1021/ma200532r},
      url          = {https://juser.fz-juelich.de/record/18197},
}