Title: Solvent controlled ion association in structured copolymers: Molecular dynamics simulations in dilute solutions

Abstract

Tailoring the nature of individual segments within ion containing block co-polymers is one critical design tool to achieve desired properties. The local structure including the size and distribution of the ionic blocks, as well as the long range correlations, are crucial for their transport ability. Here, we present molecular dynamics simulations on the effects of varying the concentrations of the ionizable groups on the conformations of pentablock ionomer that consist of a center block of ionic sulfonated styrene tethered to polyethylene and terminated by a bulky substituted styrene in dilute solutions. Sulfonation fractions f (0 ≤ f ≤ 0.55), spanning the range from ionomer to polyelectrolytes, were studied. Results for the equilibrium conformation of the chains in water and a 1:1 mixture of cyclohexane and heptane are compared to that in implicit poor solvents with dielectric constants ε = 1.0 and 77.73. In water, the pentablock collapses with the sulfonated groups on the outer surface. As f increases, the ionic, center block increasingly segregates from the hydrophobic regions. In the 1:1 mixture of cyclohexane and heptane, the flexible blocks swell, while the center ionic block collapses for f > 0. For f = 0, all blocks swell. In both implicitmore » poor solvents, the pentablock collapses into a nearly spherical shape for all f. In conclusion, the sodium counterions disperse widely throughout the simulation cell for both water and ε = 77.73, whereas for ε = 1.0 and mixture of cyclohexane and heptane, the counterions largely condense onto the collapsed pentablock.« less

Authors:

Aryal, Dipak ^[1]; Perahia, Dvora ^[1]; Grest, Gary S.  ^[2]

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+ Show Author Affiliations

1. Clemson Univ., Clemson, SC (United States)
2. Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

Publication Date:

Mon Sep 28 00:00:00 EDT 2015

Research Org.:

Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

Sponsoring Org.:

USDOE National Nuclear Security Administration (NNSA)

OSTI Identifier:

1512910

Report Number(s):

SAND-2015-7704J
Journal ID: ISSN 0021-9606; 665171

Grant/Contract Number:  

AC04-94AL85000

Resource Type:

Accepted Manuscript

Journal Name:

Journal of Chemical Physics

Additional Journal Information:

Journal Volume: 143; Journal Issue: 12; Journal ID: ISSN 0021-9606

Publisher:

American Institute of Physics (AIP)

Country of Publication:

United States

Language:

English

Subject:

74 ATOMIC AND MOLECULAR PHYSICS