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The relaxation dynamics of single flow-stretched polymers in semidilute to concentrated solutions

Tyagi, N and Cherayil, BJ (2021) The relaxation dynamics of single flow-stretched polymers in semidilute to concentrated solutions. In: Journal of Chemical Physics, 154 (2).

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Official URL: https://dx.doi.org/10.1063/5.0037513

Abstract

Recent experiments on the return to equilibrium of solutions of entangled polymers stretched by extensional flows Zhou and Schroeder, Phys. Rev. Lett. 120, 267801 (2018) have highlighted the possible role of the tube model's two-step mechanism in the process of chain relaxation. In this paper, motivated by these findings, we use a generalized Langevin equation (GLE) to study the time evolution, under linear mixed flow, of the linear dimensions of a single finitely extensible Rouse polymer in a solution of other polymers. Approximating the memory function of the GLE, which contains the details of the interactions of the Rouse polymer with its surroundings, by a power law defined by two parameters, we show that the decay of the chain's fractional extension in the steady state can be expressed in terms of a linear combination of Mittag-Leffler and generalized Mittag-Leffler functions. For the special cases of elongational flow and steady shear flow, and after adjustment of the parameters in the memory function, our calculated decay curves provide satisfactory fits to the experimental decay curves from the work of Zhou and Schroeder and earlier work of Teixeira et al. Macromolecules 40, 2461 (2007). The non-exponential character of the Mittag-Leffler functions and the consequent absence of characteristic decay constants suggest that melt relaxation may proceed by a sequence of steps with an essentially continuous, rather than discrete, spectrum of timescales. © 2021 Author(s).

Item Type: Journal Article
Publication: Journal of Chemical Physics
Publisher: American Institute of Physics Inc.
Additional Information: The copyright of this article belongs to American Institute of Physics Inc.
Keywords: Curve fitting; Differential equations; Functions; Shear flow, Concentrated solution; Fractional extensions; Generalized Langevin equation; Generalized Mittag Leffler function; Linear combinations; Mittag-Leffler functions; Relaxation dynamics; Two-step mechanisms, Polymers
Department/Centre: Division of Chemical Sciences > Inorganic & Physical Chemistry
Date Deposited: 03 Feb 2021 07:04
Last Modified: 03 Feb 2021 07:04
URI: http://eprints.iisc.ac.in/id/eprint/67798

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