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Anomalies in the coil-stretch transition of flexible polymers

Ghosal, Aishani and Cherayil, Binny J (2018) Anomalies in the coil-stretch transition of flexible polymers. In: JOURNAL OF CHEMICAL PHYSICS, 148 (9).

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Official URL: http://dx.doi.org/10.1063/1.5017555

Abstract

The flow-induced coil-stretch transition of high molecular weight polymers has generally been held to be of first order. But evidence of significant slowing down in the rate at which the polymers relax to equilibrium in the vicinity of the transition suggests that the thermodynamic character of the transition may be less clear-cut. The above slowing down effect is actually characteristic of a second-order transition, and it points to the existence of a broad spectrum of conformational states in the transition region, analogous to the existence of fluctuations of all length scales at a critical point. In this paper, using a path integral approach based on a free-draining finitely extensible chain model, we calculate various polymer properties as a function of elongational flow as a way of exploring different statistical mechanical details of the coil-stretch transition. These properties include the molecular weight dependence of the flow-extension curve of the polymer, the distribution of its steady-state end-to-end distances, and the characteristic relaxation time tau(R) of these distances. Among other findings, our calculations indicate that the coil-stretch transition is discontinuous in the N -> infinity limit, that the effective free energy of the chain is unimodal at all values of the flow, becoming broad and flat in the immediate vicinity of the transition, and that the ratio of tau(R) to the Rouse relaxation time increases abruptly at the transition before eventually reaching a plateau value at large flow strengths. These aspects of the coil-stretch transition place it among a larger class of unconventional nominally first-order single chain transitions that include the adsorption transition of surface-tethered polymers and the escape transition of compressed polymers. Published by AIP Publishing.

Item Type: Journal Article
Additional Information: Copy right for the article belong to AMER INST PHYSICS, 1305 WALT WHITMAN RD, STE 300, MELVILLE, NY 11747-4501 USA
Department/Centre: Division of Chemical Sciences > Inorganic & Physical Chemistry
Depositing User: Id for Latest eprints
Date Deposited: 02 Apr 2018 19:57
Last Modified: 02 Apr 2018 19:57
URI: http://eprints.iisc.ac.in/id/eprint/59446

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