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Poly (N-isopropylacrylamide) response to salt concentration and anion identity: a brush-on-brush study

Humphreys, Ben A LU ; Johnson, Edwin C ; Wanless, Erica J and Webber, Grant B (2019) In Langmuir 35(33). p.10818-10830
Abstract
The stability of poly(N-isopropylacrylamide) (PNIPAM) brush-modified colloidal silica particles was compared to asymmetric and symmetric PNIPAM brush direct force measurements in the presence of 1, 10, and 500 mM aqueous salt solution of KCl, KNO3, and KSCN between 10 and 45 °C. Dynamic light scattering measurements highlighted subtle variations in the salt-mediated thermoresponse, while atomic force microscopy (AFM) force curves between a bare silica or PNIPAM brush-modified colloid probe and a planar PNIPAM brush elucidated differences in brush interactions. The AFM force curves in the presence of KCl primarily revealed steric interactions between the surfaces, while KNO3 and KSCN solutions exhibited... (More)
The stability of poly(N-isopropylacrylamide) (PNIPAM) brush-modified colloidal silica particles was compared to asymmetric and symmetric PNIPAM brush direct force measurements in the presence of 1, 10, and 500 mM aqueous salt solution of KCl, KNO3, and KSCN between 10 and 45 °C. Dynamic light scattering measurements highlighted subtle variations in the salt-mediated thermoresponse, while atomic force microscopy (AFM) force curves between a bare silica or PNIPAM brush-modified colloid probe and a planar PNIPAM brush elucidated differences in brush interactions. The AFM force curves in the presence of KCl primarily revealed steric interactions between the surfaces, while KNO3 and KSCN solutions exhibited electrosteric interactions on approach as a function of the chaotropic nature of the ion and the solution concentration. The symmetric PNIPAM brush interaction highlighted significant variations between KCl and KSCN at 1 and 500 mM concentrations, while the approach and retraction force curves were relatively similar at 10 mM concentration. The combination of these techniques enabled the stability of PNIPAM brush-modified colloidal dispersions in the presence of electrolyte to be better understood with specific ion binding and the solution Debye length playing a significant role. (Less)
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author
; ; and
publishing date
type
Contribution to journal
publication status
published
subject
in
Langmuir
volume
35
issue
33
pages
13 pages
publisher
The American Chemical Society (ACS)
external identifiers
  • scopus:85071045745
ISSN
0743-7463
DOI
10.1021/acs.langmuir.9b00695
language
English
LU publication?
no
id
58fa934f-01c0-4d7e-b1d2-66f8ea3a8fb2
date added to LUP
2022-04-01 21:03:47
date last changed
2022-06-24 04:05:42
@article{58fa934f-01c0-4d7e-b1d2-66f8ea3a8fb2,
  abstract     = {{The stability of poly(<i>N</i>-isopropylacrylamide) (PNIPAM) brush-modified colloidal silica particles was compared to asymmetric and symmetric PNIPAM brush direct force measurements in the presence of 1, 10, and 500 mM aqueous salt solution of KCl, KNO<sub>3</sub>, and KSCN between 10 and 45 °C. Dynamic light scattering measurements highlighted subtle variations in the salt-mediated thermoresponse, while atomic force microscopy (AFM) force curves between a bare silica or PNIPAM brush-modified colloid probe and a planar PNIPAM brush elucidated differences in brush interactions. The AFM force curves in the presence of KCl primarily revealed steric interactions between the surfaces, while KNO<sub>3</sub> and KSCN solutions exhibited electrosteric interactions on approach as a function of the chaotropic nature of the ion and the solution concentration. The symmetric PNIPAM brush interaction highlighted significant variations between KCl and KSCN at 1 and 500 mM concentrations, while the approach and retraction force curves were relatively similar at 10 mM concentration. The combination of these techniques enabled the stability of PNIPAM brush-modified colloidal dispersions in the presence of electrolyte to be better understood with specific ion binding and the solution Debye length playing a significant role.}},
  author       = {{Humphreys, Ben A and Johnson, Edwin C and Wanless, Erica J and Webber, Grant B}},
  issn         = {{0743-7463}},
  language     = {{eng}},
  number       = {{33}},
  pages        = {{10818--10830}},
  publisher    = {{The American Chemical Society (ACS)}},
  series       = {{Langmuir}},
  title        = {{Poly (<i>N</i>-isopropylacrylamide) response to salt concentration and anion identity: a brush-on-brush study}},
  url          = {{http://dx.doi.org/10.1021/acs.langmuir.9b00695}},
  doi          = {{10.1021/acs.langmuir.9b00695}},
  volume       = {{35}},
  year         = {{2019}},
}