Topological effects in ring polymers. II. Influence of persistence length

M Muller, J P Wittmer, M E Cates

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The interplay of topological constraints and the persistence length of ring polymers in their own melt is investigated by means of dynamical Monte Carlo simulations of a three-dimensional lattice model. We ask if the results are consistent with an asymptotically regime where the rings behove like (compact) lattice anumals, in a self-consistent network of topological constraints imposed by neighboring rings. Tuning the persistence length provides an efficient route to increase the ring overlap required for this mean-field picture to hold: The effective Flory exponent for the ring size decreases down to v less than or equal to 1/3 with increasing persistence length. Evidence is provided for the emergence of one additional characteristic length scale d,proportional to N-0, only weakly dependent on the persistence length and much larger than the excluded volume screening length xi. At distances larger than d, the conformational properties of the rings are governed by the topological interactions; at smaller distances rings and their linear chain counterparts become similar. (At distances smaller than xi both architectures are identical.) However, the crossover between both limits is intricate and broad? as a detailed discussion of the local fractal dimension (e.g., obtained from the static structure factor) reveals. This is due to various crossover effects which we are unable to separate even for the largest ring size (N = 1024) presented here. The increased topological interactions also influence the dynamical properties, Mean-square displacements and their distributions depend crucially on the ring overlap, and show evidence of the existence of additional size rind time scales. The diffusion constant of the rings goes down from effectively D(N)proportional to N-1.22 for flexible rings with low overlap to D(N)proportional to N-1.68 for strongly overlapping semiflexible rings.

Original languageEnglish
Pages (from-to)4078-4089
Number of pages12
JournalPhysical review E: Statistical physics, plasmas, fluids, and related interdisciplinary topics
Issue number4
Publication statusPublished - Apr 2000


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