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Heterogeneous dynamics of unentangled chains in polymer nanocomposites
writer:L.-J. Dai, C.-L. Fu, Y.-L. Zhu, Z.-Y. Sun
keywords:Polymer nanocomposites
specific source:J. Chem. Phys. 150, 184903 (2019)
Issue time:2019年
We present a systematic investigation on the effect of adding nanoparticles on the dynamics of polymer chains by using coarse-grained molecular dynamics simulation. The dynamics is characterized by three aspects: molecular motion, relaxation at different length scales, and dynamical heterogeneity. It is found that the motion of polymer chains slows down and the deviation from Gaussian distribution becomes more pronounced with increasing nanoparticle volume fractions. For polymer nanocomposites with R ≤ Rg, the relaxation at the wave vector q = 7.0 displays multistep decay, consistent with the previous reports in strongly interacting polymer nanocomposites. Moreover, a qualitatively universal law is established that dynamic heterogeneity at whole chain''''s scale follows a nonmonotonic increase with increasing nanoparticle loadings, where the volume fraction of the maximum dynamic heterogeneity corresponds to the particle loading when the average distance between nanoparticles is equal to the Kuhn length of polymer chains. We show that the decoupling between whole chain''''s dynamics and segment dynamics is responsible for the nonmonotonic behavior of dynamic heterogeneity of whole chains. Published under license by AIP Publishing. https://doi.