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A Monte Carlo study of titrating polyelectrolytes

Ullner, Magnus LU ; Jönsson, Bo LU ; Söderberg, Bo LU and Peterson, Carsten LU (1996) In Journal of Chemical Physics 104(8). p.3048-3057
Abstract

Monte Carlo simulations have been used to study three different models for linear, titrating polyelectrolytes in a salt-free environment: (i) a rigid polymer with rigid bonds (rigid rod); (ii) a flexible polymer with rigid bonds; and (iii) a flexible polymer with flexible bonds. The use of a very efficient pivot algorithm has made it possible to simulate very long chains, with up to several thousand titrating groups. The results have been compared to a mean field approximation for a rigid rod and variational results emanating from a Flory type approach. It is found that the rigid rod mean field model gives a qualitatively correct description for the apparent dissociation constant for all three models. At room temperature, the energy... (More)

Monte Carlo simulations have been used to study three different models for linear, titrating polyelectrolytes in a salt-free environment: (i) a rigid polymer with rigid bonds (rigid rod); (ii) a flexible polymer with rigid bonds; and (iii) a flexible polymer with flexible bonds. The use of a very efficient pivot algorithm has made it possible to simulate very long chains, with up to several thousand titrating groups. The results have been compared to a mean field approximation for a rigid rod and variational results emanating from a Flory type approach. It is found that the rigid rod mean field model gives a qualitatively correct description for the apparent dissociation constant for all three models. At room temperature, the energy contribution to the apparent dissociation constant often dominates over the entropic term, which partly explains the relative success of this approach. In the case of flexible bonds, both the conformational behavior and the behavior of the apparent dissociation constant are well described by a variational ansatz with a quadratic term, largely thanks to the harmonicity of the bonds themselves. The approach is less successful for rigid bonds, which becomes evident for highly charged chains where a harmonic entropy term is incorrect. This can be remedied by replacing it with an expression valid in the strong coupling regime. Empirical scaling expressions have also been found, primarily for the end-to-end distance. © 1996 American Institute of Physics.

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organization
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type
Contribution to journal
publication status
published
subject
in
Journal of Chemical Physics
volume
104
issue
8
pages
10 pages
publisher
American Institute of Physics
external identifiers
  • Scopus:0001146345
ISSN
0021-9606
DOI
10.1063/1.471071
language
English
LU publication?
yes
id
1e566027-87db-4eab-bc5e-55b3e515034d
date added to LUP
2016-10-03 19:20:01
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2017-01-03 10:03:23
@article{1e566027-87db-4eab-bc5e-55b3e515034d,
  abstract     = {<p>Monte Carlo simulations have been used to study three different models for linear, titrating polyelectrolytes in a salt-free environment: (i) a rigid polymer with rigid bonds (rigid rod); (ii) a flexible polymer with rigid bonds; and (iii) a flexible polymer with flexible bonds. The use of a very efficient pivot algorithm has made it possible to simulate very long chains, with up to several thousand titrating groups. The results have been compared to a mean field approximation for a rigid rod and variational results emanating from a Flory type approach. It is found that the rigid rod mean field model gives a qualitatively correct description for the apparent dissociation constant for all three models. At room temperature, the energy contribution to the apparent dissociation constant often dominates over the entropic term, which partly explains the relative success of this approach. In the case of flexible bonds, both the conformational behavior and the behavior of the apparent dissociation constant are well described by a variational ansatz with a quadratic term, largely thanks to the harmonicity of the bonds themselves. The approach is less successful for rigid bonds, which becomes evident for highly charged chains where a harmonic entropy term is incorrect. This can be remedied by replacing it with an expression valid in the strong coupling regime. Empirical scaling expressions have also been found, primarily for the end-to-end distance. © 1996 American Institute of Physics.</p>},
  author       = {Ullner, Magnus and Jönsson, Bo and Söderberg, Bo and Peterson, Carsten},
  issn         = {0021-9606},
  language     = {eng},
  number       = {8},
  pages        = {3048--3057},
  publisher    = {American Institute of Physics},
  series       = {Journal of Chemical Physics},
  title        = {A Monte Carlo study of titrating polyelectrolytes},
  url          = {http://dx.doi.org/10.1063/1.471071},
  volume       = {104},
  year         = {1996},
}