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Combined experimental and theoretical study of weak polyelectrolyte brushes in salt mixtures

Willott, Joshua D ; Humphreys, Ben A LU ; Webber, Grant B ; Wanless, Erica J and de Vos, Wiebe M (2019) In Langmuir 35(7). p.2709-2718
Abstract
The swelling behavior of a hydrophobic poly(2diisopropylamino)ethyl methacrylate (PDPA) brush immersed in aqueous solutions of single and mixed salts has been investigated using ellipsometry and numerical self-consistent field (nSCF) theory. As a function of solution ionic strength, the osmotic and salted brush regimes of weak polyelectrolyte brushes as well as substantial specific anion effects in the presence of K+ salts of Cl–, NO3–, and SCN– are found. For solutions containing mixtures of NO3– and Cl–, the brush swelling is the same as one would expect on the basis of the concentration-weighted average of the brush behavior in the single salt... (More)
The swelling behavior of a hydrophobic poly(2diisopropylamino)ethyl methacrylate (PDPA) brush immersed in aqueous solutions of single and mixed salts has been investigated using ellipsometry and numerical self-consistent field (nSCF) theory. As a function of solution ionic strength, the osmotic and salted brush regimes of weak polyelectrolyte brushes as well as substantial specific anion effects in the presence of K+ salts of Cl–, NO3–, and SCN– are found. For solutions containing mixtures of NO3– and Cl–, the brush swelling is the same as one would expect on the basis of the concentration-weighted average of the brush behavior in the single salt solutions. However, in mixtures of SCN– and Cl–, the swelling response is more complicated and substantial divergence from ideal behavior is observed. Mean-field theory shows excellent qualitative agreement with the ellipsometry findings. nSCF reveals that for the SCN–/Cl– cases the swelling behavior of the PDPA brush most likely arises from the predominant localization of the weakly hydrated SCN– within the brush compared to the more strongly hydrated Cl–. (Less)
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author
; ; ; and
publishing date
type
Contribution to journal
publication status
published
subject
in
Langmuir
volume
35
issue
7
pages
10 pages
publisher
The American Chemical Society (ACS)
external identifiers
  • scopus:85061556335
ISSN
0743-7463
DOI
10.1021/acs.langmuir.8b03838
language
English
LU publication?
no
id
e9a968f4-b79a-45bf-99be-2b36b0fa78e1
date added to LUP
2022-04-01 21:05:43
date last changed
2022-04-22 00:27:23
@article{e9a968f4-b79a-45bf-99be-2b36b0fa78e1,
  abstract     = {{The swelling behavior of a hydrophobic poly(2diisopropylamino)ethyl methacrylate (PDPA) brush immersed in aqueous solutions of single and mixed salts has been investigated using ellipsometry and numerical self-consistent field (nSCF) theory. As a function of solution ionic strength, the osmotic and salted brush regimes of weak polyelectrolyte brushes as well as substantial specific anion effects in the presence of K<sup>+</sup> salts of Cl<sup>–</sup>, NO<sub>3</sub><sup>–</sup>, and SCN<sup>–</sup> are found. For solutions containing mixtures of NO<sub>3</sub><sup>–</sup> and Cl<sup>–</sup>, the brush swelling is the same as one would expect on the basis of the concentration-weighted average of the brush behavior in the single salt solutions. However, in mixtures of SCN<sup>–</sup> and Cl<sup>–</sup>, the swelling response is more complicated and substantial divergence from ideal behavior is observed. Mean-field theory shows excellent qualitative agreement with the ellipsometry findings. nSCF reveals that for the SCN<sup>–</sup>/Cl<sup>–</sup> cases the swelling behavior of the PDPA brush most likely arises from the predominant localization of the weakly hydrated SCN<sup>–</sup> within the brush compared to the more strongly hydrated Cl<sup>–</sup>.}},
  author       = {{Willott, Joshua D and Humphreys, Ben A and Webber, Grant B and Wanless, Erica J and de Vos, Wiebe M}},
  issn         = {{0743-7463}},
  language     = {{eng}},
  number       = {{7}},
  pages        = {{2709--2718}},
  publisher    = {{The American Chemical Society (ACS)}},
  series       = {{Langmuir}},
  title        = {{Combined experimental and theoretical study of weak polyelectrolyte brushes in salt mixtures}},
  url          = {{http://dx.doi.org/10.1021/acs.langmuir.8b03838}},
  doi          = {{10.1021/acs.langmuir.8b03838}},
  volume       = {{35}},
  year         = {{2019}},
}