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@INPROCEEDINGS{Richter:1046464,
      author       = {Richter, Dieter and Kruteva, Margarita and Allgaier,
                      Jürgen and Monkenbusch, Michael and Hoffmann, Ingo and
                      Peponaki, Katerina and Vlassopoulos, Dimitri},
      title        = {{N}eutron {I}nvestigations on the {S}tructure and dynamics
                      of ring-linear polymer blends},
      reportid     = {FZJ-2025-03817},
      year         = {2025},
      abstract     = {Blends of ring and linear polymers pose fascinating
                      challenges. While in such blends the dynamics of linear
                      chains is hardly affected, already minute concentrations of
                      linear chains have a large effect on ring rheology /1/.
                      Blends of rings with linear chains are characterized by
                      strong interpenetration of the rings by the linear chains.
                      These threadings swell the ring conformation significantly
                      and alter the ring dynamics very strongly, as large scale
                      ring motions are only possible by constraint release of the
                      linear component /2/. We have performed systematic Small
                      Angle Neutron Scattering (SANS) investigation of such
                      blends, where we have varied the ring volume fraction $ϕ_R$
                      for a ring 40 kg/mol polyethylene-oxide (PEO) in a linear
                      matrix of 100 kg/mol. We found that with increasing ring
                      fraction the ring radius of gyration ( $R_g)$ swells by more
                      than $20\%$ . At the same time the fractal dimension, which
                      is close to a Gaussian conformation at low $ϕ_R,$ decreases
                      to the value of the ring melt. Following a random phase
                      approximation (RPA) treatment, the Flory-Huggins parameter
                      $(χ_F)$ is large, negative and independent of $ϕ_R,$
                      signifying ring-linear attraction leading to ringring
                      repulsion /3/. Concerning the ring dynamics in symmetric
                      ring/linear blends of 40kg/mol PEO as a function of $ϕ_R$
                      we observed a transformation of typical self-similar ring
                      relaxation to local reptation type dynamics at higher linear
                      fraction, where the motion of the ring is slaved by the
                      linear host. The cross-over between the two types of motions
                      takes place for 0.25 $<ϕ_R<0.5.$ Even though at $ϕ_R=0.5$
                      the characteristic spectral shape assumes the local
                      reptation scheme, the actual constraints expressed by the
                      apparent entanglement length Ne are less than those at
                      higher linear volume fraction $(N_e100$ compared to $N_e70$
                      for $ϕ_R≤0.35.$ In addition ring mode suppression is
                      observed: A detailed mode analysis of the neat ring melt as
                      well as the $ϕ_(R$ )=0.95 blend revealed a suppression of
                      the first ring p = 2 mode. For $ϕ_(R$ )=0.75 also the
                      second ring mode p = 4 is suppressed. The p = 2 mode length
                      scale comprises the full ring size; it suppression already
                      in the neat melt indicates significant constraints on the
                      ring motion beyond the self-similar mode structure. This
                      observation correlates with the non- exponential decal of
                      dynamic shear modulus at long times, which is attributed to
                      ring-ring threading. References 1 M. Kapnistos, M. Lang, D.
                      Vlassopoulos, W. Pyckhout-Hintzen, D. Richter, D. Cho,
                      T.Chang, M. Rubinstein, Nature Materials 7, 997-1002 (2008)
                      2 Margarita Kruteva, Jürgen Allgaier and Dieter Richter,
                      Macromolecules, 56, 7203 - 7229 (2023) 3 M. Kruteva, M.
                      Monkenbusch, J. Allgaier, L. Porcar, D. Richter,
                      Macromolecules, 56, 4835 – 4844 (2023)},
      month         = {Sep},
      date          = {2025-09-29},
      organization  = {9th International Soft Matter
                       Conference, Minoa Palace Hotel and
                       conference center, outside the city of
                       Chania in Western Crete (Greece), 29
                       Sep 2025 - 3 Oct 2025},
      subtyp        = {Invited},
      cin          = {JCNS-2 / JARA-FIT / JCNS-1},
      cid          = {I:(DE-Juel1)JCNS-2-20110106 / $I:(DE-82)080009_20140620$ /
                      I:(DE-Juel1)JCNS-1-20110106},
      pnm          = {632 - Materials – Quantum, Complex and Functional
                      Materials (POF4-632) / 6G4 - Jülich Centre for Neutron
                      Research (JCNS) (FZJ) (POF4-6G4)},
      pid          = {G:(DE-HGF)POF4-632 / G:(DE-HGF)POF4-6G4},
      typ          = {PUB:(DE-HGF)6},
      url          = {https://juser.fz-juelich.de/record/1046464},
}