APS March Meeting 2016
Volume 61, Number 2
Monday–Friday, March 14–18, 2016;
Baltimore, Maryland
Session F4: Polymer Architecture Effects on Structure Dynamics
11:15 AM–2:15 PM,
Tuesday, March 15, 2016
Room: Ballroom IV
Sponsoring
Unit:
DPOLY
Chair: Michael Rubinstein, Univ of NC - Chapel Hill
Abstract ID: BAPS.2016.MAR.F4.3
Abstract: F4.00003 : Self-Similar Conformations and Dynamics of Non-Concatenated Entangled Ring Polymers*
12:27 PM–1:03 PM
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Abstract
Author:
Ting Ge
(University of North Carolina at Chapel Hill)
A scaling model of self-similar conformations and dynamics of
non-concatenated entangled ring polymers is developed. Topological
constraints force these ring polymers into compact conformations with
fractal dimension D$=$3 that we call fractal loopy globules (FLGs). This
result is based on the conjecture that the overlap parameter of loops on all
length scales is equal to the Kavassalis-Noolandi number 10-20. The dynamics
of entangled rings is self-similar, and proceeds as loops of increasing
sizes are rearranged progressively at their respective diffusion times. The
topological constraints associated with smaller rearranged loops affect the
dynamics of larger loops by increasing the effective friction coefficient,
but have no influence on the tubes confining larger loops. Therefore, the
tube diameter defined as the average spacing between relevant topological
constraints increases with time, leading to ``tube dilation''. Analysis of
the primitive paths in molecular dynamics (MD) simulations suggests complete
tube dilation with the tube diameter on the order of the time-dependent
characteristic loop size. A characteristic loop at time t is defined as a
ring section that has diffused a distance of its size during time t. We
derive dynamic scaling exponents in terms of fractal dimensions of an
entangled ring and the underlying primitive path and a parameter
characterizing the extent of tube dilation. The results reproduce the
predictions of different dynamic models of a single non-concatenated
entangled ring. We demonstrate that traditional generalization of
single-ring models to multi-ring dynamics is not self-consistent and develop
a FLG model with self-consistent multi-ring dynamics and complete tube
dilation. Various dynamic scaling exponents predicted by the self-consistent
FLG model are consistent with recent computer simulations and experiments.
We also perform MD simulations of nanoparticle (NP) diffusion in melts of
non-concatenated entangled ring polymers. NPs larger than the undilated tube
diameter undergo power-law sub-diffusion in entangled rings in contrast to
strong suppression in entangled linear chains. This result demonstrates that
there is no long-lived confining tube in entangled ring polymers, which
agrees with complete tube dilation in the self-consistent FLG model.
*This work is done in collaboration with Drs. Michael Rubinstein, Sergey Panyukov and Gary Grest and supported by NSF.
To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2016.MAR.F4.3