%0 Conference Paper
%A Richter, Dieter
%A Kruteva, Margarita
%A Allgaier, Jürgen
%A Monkenbusch, Michael
%A Hoffmann, Ingo
%A Peponaki, Katerina
%A Vlassopoulos, Dimitri
%T Neutron Investigations on the Structure and dynamics of ring-linear polymer blends
%M FZJ-2025-03817
%D 2025
%X 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)
%B 9th International Soft Matter Conference
%C 29 Sep 2025 - 3 Oct 2025, Minoa Palace Hotel and conference center, outside the city of Chania in Western Crete (Greece)
Y2 29 Sep 2025 - 3 Oct 2025
M2 Minoa Palace Hotel and conference center, outside the city of Chania in Western Crete, Greece
%F PUB:(DE-HGF)6
%9 Conference Presentation
%U https://juser.fz-juelich.de/record/1046464