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Title: Comparing solvophobic and multivalent induced collapse in polyelectrolyte brushes

Abstract

Here, coarse-grained molecular dynamics enhanced by free-energy sampling methods is used to examine the roles of solvophobicity and multivalent salts on polyelectrolyte brush collapse. Specifically, we demonstrate that while ostensibly similar, solvophobic collapsed brushes and multivalent-ion collapsed brushes exhibit distinct mechanistic and structural features. Notably, multivalent-induced heterogeneous brush collapse is observed under good solvent polymer backbone conditions, demonstrating that the mechanism of multivalent collapse is not contingent upon a solvophobic backbone. Umbrella sampling of the potential of mean-force (PMF) between two individual brush strands confirms this analysis, revealing starkly different PMFs under solvophobic and multivalent conditions, suggesting the role of multivalent “bridging” as the discriminating feature in trivalent collapse. Structurally, multivalent ions show a propensity for nucleating order within collapsed brushes, whereas poor-solvent collapsed brushes are more disordered; this difference is traced to the existence of a metastable PMF minimum for poor solvent conditions, and a global PMF minimum for trivalent systems, under experimentally relevant conditions.

Authors:
 [1]; ORCiD logo [2];  [3];  [1]; ORCiD logo [1]
  1. The Univ. of Chicago, Chicago, IL (United States); Argonne National Lab. (ANL), Lemont, IL (United States)
  2. The Univ. of Chicago, Chicago, IL (United States)
  3. Argonne National Lab. (ANL), Lemont, IL (United States)
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1351285
Grant/Contract Number:  
AC02-06CH11357
Resource Type:
Accepted Manuscript
Journal Name:
ACS Macro Letters
Additional Journal Information:
Journal Volume: 6; Journal Issue: 2; Journal ID: ISSN 2161-1653
Publisher:
American Chemical Society (ACS)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; polyelectrolytes

Citation Formats

Jackson, Nicholas E., Brettmann, Blair K., Vishwanath, Venkatram, Tirrell, Matthew, and de Pablo, Juan J. Comparing solvophobic and multivalent induced collapse in polyelectrolyte brushes. United States: N. p., 2017. Web. doi:10.1021/acsmacrolett.6b00837.
Jackson, Nicholas E., Brettmann, Blair K., Vishwanath, Venkatram, Tirrell, Matthew, & de Pablo, Juan J. Comparing solvophobic and multivalent induced collapse in polyelectrolyte brushes. United States. doi:10.1021/acsmacrolett.6b00837.
Jackson, Nicholas E., Brettmann, Blair K., Vishwanath, Venkatram, Tirrell, Matthew, and de Pablo, Juan J. Fri . "Comparing solvophobic and multivalent induced collapse in polyelectrolyte brushes". United States. doi:10.1021/acsmacrolett.6b00837. https://www.osti.gov/servlets/purl/1351285.
@article{osti_1351285,
title = {Comparing solvophobic and multivalent induced collapse in polyelectrolyte brushes},
author = {Jackson, Nicholas E. and Brettmann, Blair K. and Vishwanath, Venkatram and Tirrell, Matthew and de Pablo, Juan J.},
abstractNote = {Here, coarse-grained molecular dynamics enhanced by free-energy sampling methods is used to examine the roles of solvophobicity and multivalent salts on polyelectrolyte brush collapse. Specifically, we demonstrate that while ostensibly similar, solvophobic collapsed brushes and multivalent-ion collapsed brushes exhibit distinct mechanistic and structural features. Notably, multivalent-induced heterogeneous brush collapse is observed under good solvent polymer backbone conditions, demonstrating that the mechanism of multivalent collapse is not contingent upon a solvophobic backbone. Umbrella sampling of the potential of mean-force (PMF) between two individual brush strands confirms this analysis, revealing starkly different PMFs under solvophobic and multivalent conditions, suggesting the role of multivalent “bridging” as the discriminating feature in trivalent collapse. Structurally, multivalent ions show a propensity for nucleating order within collapsed brushes, whereas poor-solvent collapsed brushes are more disordered; this difference is traced to the existence of a metastable PMF minimum for poor solvent conditions, and a global PMF minimum for trivalent systems, under experimentally relevant conditions.},
doi = {10.1021/acsmacrolett.6b00837},
journal = {ACS Macro Letters},
number = 2,
volume = 6,
place = {United States},
year = {2017},
month = {2}
}

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