Nanoparticle dynamics in semidilute polymer solutions: Rings versus linear chains

RJ Chen and SB Kotkar and R Poling-Skutvik and MP Howard and A Nikoubashman and JC Conrad and JC Palmer, JOURNAL OF RHEOLOGY, 65, 745-755 (2021).

DOI: 10.1122/8.0000223

We study the dynamics of nanoparticles in semidilute solutions of ring and linear polymers using hybrid molecular dynamics-multiparticle collision dynamics simulations. The dynamics of the monomers, the polymer centers-of-mass, and the nanoparticles coincide for these two architectures for solutions of the same monomer concentration. The long time diffusivities of the nanoparticles follow the predictions of a polymer coupling theory Cai et al., Macromolecules 44, 7853-7863 (2011), suggesting that nanoparticle dynamics are coupled to segmental relaxations for both polymer architectures examined here. At intermediate time scales, the nanoparticle dynamics are characterized by subdiffusive exponents, which markedly deviate from coupling theory and closely follow those of the polymers. Instead, the nanoparticle dynamics are strongly coupled to the polymer center-of-mass motions for both architectures, rather than to their segmental dynamics. The presence of ring concatenations does not affect the long-time diffusivity of the nanoparticles but leads to a slight decrease in the subdiffusive exponents of the nanoparticles and the polymer center-of-mass. (C) 2021 The Society of Rheology.

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