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Polyelectrolyte adsorption: electrostatic mechanisms and nonmonotonic responses to salt addition.

Forsman, Jan LU (2012) In Langmuir 28(11). p.5138-5150
Abstract
The main question addressed in this work is as follows: Under pure electrosorption conditions, that is, disregarding nonelectrostatic effects, how does the net adsorption of a polyelectrolyte at an oppositely charged surface respond to the addition of simple salt? Previous simulations and mean-field calculations have suggested that the polymers will desorb. However, we will demonstrate that an increased adsorption also is possible, even for pure electrosorption, at low and intermediate levels of salt. As this is a correlation-driven effect, mean field approaches will fail to capture it. Using simulations, one will in general need to simulate large systems and relatively long polymers. Also important is the presence of a proper bulk... (More)
The main question addressed in this work is as follows: Under pure electrosorption conditions, that is, disregarding nonelectrostatic effects, how does the net adsorption of a polyelectrolyte at an oppositely charged surface respond to the addition of simple salt? Previous simulations and mean-field calculations have suggested that the polymers will desorb. However, we will demonstrate that an increased adsorption also is possible, even for pure electrosorption, at low and intermediate levels of salt. As this is a correlation-driven effect, mean field approaches will fail to capture it. Using simulations, one will in general need to simulate large systems and relatively long polymers. Also important is the presence of a proper bulk solution, with a finite and well-defined polyelectrolyte concentration. We have performed a theoretical study of polyelectrolyte adsorption, assuming screened Coulomb interactions between monomers; that is, the salt is implicit. This work focuses on the effects from ionic screening and polymer length. Specifically, the adsorption at a weakly charged colloidal particle, with a diameter of 200 nm, is monitored for various salt concentrations, in the presence of highly charged chains. Using simulations, we investigate polymers with two different degrees of polymerization: 40 and 160, respectively. These simulations are complemented by predictions from classical polymer density functional theory, utilizing a recently developed correlation-correction (Forsman, J.; Nordholm, S. Langmuir, in press). The agreement with corresponding simulations is semiquantitative, and because the calculations run many orders of magnitude faster than the simulations, longer and more realistic polymers could be studied with this approach. However, switching off the correlation-correction leads to a mean-field theory, which fails to even qualitatively reproduce the simulated response to screening. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Langmuir
volume
28
issue
11
pages
5138 - 5150
publisher
The American Chemical Society
external identifiers
  • wos:000301636900029
  • pmid:22360456
  • scopus:84858780439
ISSN
0743-7463
DOI
10.1021/la3000735
language
English
LU publication?
yes
id
2dc0cad9-a9c5-488f-a04b-89c6a3121576 (old id 2432551)
alternative location
http://www.ncbi.nlm.nih.gov/pubmed/22360456?dopt=Abstract
date added to LUP
2012-04-04 11:53:36
date last changed
2017-09-17 04:21:53
@article{2dc0cad9-a9c5-488f-a04b-89c6a3121576,
  abstract     = {The main question addressed in this work is as follows: Under pure electrosorption conditions, that is, disregarding nonelectrostatic effects, how does the net adsorption of a polyelectrolyte at an oppositely charged surface respond to the addition of simple salt? Previous simulations and mean-field calculations have suggested that the polymers will desorb. However, we will demonstrate that an increased adsorption also is possible, even for pure electrosorption, at low and intermediate levels of salt. As this is a correlation-driven effect, mean field approaches will fail to capture it. Using simulations, one will in general need to simulate large systems and relatively long polymers. Also important is the presence of a proper bulk solution, with a finite and well-defined polyelectrolyte concentration. We have performed a theoretical study of polyelectrolyte adsorption, assuming screened Coulomb interactions between monomers; that is, the salt is implicit. This work focuses on the effects from ionic screening and polymer length. Specifically, the adsorption at a weakly charged colloidal particle, with a diameter of 200 nm, is monitored for various salt concentrations, in the presence of highly charged chains. Using simulations, we investigate polymers with two different degrees of polymerization: 40 and 160, respectively. These simulations are complemented by predictions from classical polymer density functional theory, utilizing a recently developed correlation-correction (Forsman, J.; Nordholm, S. Langmuir, in press). The agreement with corresponding simulations is semiquantitative, and because the calculations run many orders of magnitude faster than the simulations, longer and more realistic polymers could be studied with this approach. However, switching off the correlation-correction leads to a mean-field theory, which fails to even qualitatively reproduce the simulated response to screening.},
  author       = {Forsman, Jan},
  issn         = {0743-7463},
  language     = {eng},
  number       = {11},
  pages        = {5138--5150},
  publisher    = {The American Chemical Society},
  series       = {Langmuir},
  title        = {Polyelectrolyte adsorption: electrostatic mechanisms and nonmonotonic responses to salt addition.},
  url          = {http://dx.doi.org/10.1021/la3000735},
  volume       = {28},
  year         = {2012},
}