Unusual dynamics of ring probes in linear matrices |
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| Authors: | Sachin Shanbhag |
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| Affiliation: | Department of Scientific Computing, Florida State University, Tallahassee, Florida |
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| Abstract: | We perform Monte Carlo simulations of ring and linear polymers in linear matrices, and investigate the diffusivity of the probes. As the matrix chain length Nm is increased from 10 to 300 monomers, the diffusivity Dl of a linear probe (Nl = 300) decreases monotonically, while that of a ring probe Dr varies non‐monotonically, with a peak around  . We perform additional simulations with a single probe molecule (  ) in a linear matrix (  ). The non‐monotonicity in Dr persists even after ring–ring interactions are eliminated. Topology dependent differences in the short‐time dynamics of the probes are observed; unlike linear probes, mean‐squared displacements of ring probes depend on Nm. Primitive path analysis suggests that the difference in dynamics originates from differences in entanglement structure. For linear probes, the degree of entanglement is independent of Nm. For ring probes, we observe two regimes: when Nm is small, the number of threadings decreases as Nm increases, eventually transitioning to a plateau. In the small Nm regime, the change in the degree of entanglement offsets the change in the mobility of the matrix chains, leading to a non‐monotonic variation in Dr. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 169–177 |
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| Keywords: | diffusion macrocyclics Monte Carlo simulation ring polymer tracer diffusion |
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. We perform additional simulations with a single probe molecule ( 
) in a linear matrix ( 
). The non‐monotonicity in Dr persists even after ring–ring interactions are eliminated. Topology dependent differences in the short‐time dynamics of the probes are observed; unlike linear probes, mean‐squared displacements of ring probes depend on Nm. Primitive path analysis suggests that the difference in dynamics originates from differences in entanglement structure. For linear probes, the degree of entanglement is independent of Nm. For ring probes, we observe two regimes: when Nm is small, the number of threadings decreases as Nm increases, eventually transitioning to a plateau. In the small Nm regime, the change in the degree of entanglement offsets the change in the mobility of the matrix chains, leading to a non‐monotonic variation in Dr. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 169–177