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Enrichment of charged monomers explains non-monotonic polymer volume fraction profiles of multi-stimulus responsive copolymer brushes

Johnson, Edwin C ; Willott, Joshua D ; Gresham, Isaac J ; Murdoch, Timothy J ; Humphreys, Ben A LU ; Prescott, Stuart W ; Nelson, Andrew ; de Vos, Wiebe M ; Webber, Grant B and Wanless, Erica J (2020) In Langmuir 36(42). p.12460-12472
Abstract
Multi-stimulus responsive poly(2-(2-methoxyethoxy)ethyl methacrylate-co-2-(diethylamino)ethyl methacrylate) [P(MEO2MA-co-DEA)] 80:20 mol % copolymer brushes were synthesized on planar silica substrates via surface-initiated activators continuously regenerated via electron transfer atom transfer radical polymerization. Brush thickness was sensitive to changes in pH and temperature as monitored with ellipsometry. At low pH, the brush is charged and swollen, while at high pH, the brush is uncharged and more collapsed. Clear thermoresponsive behavior is also observed with the brush more swollen at low temperatures compared to high temperatures at both high and low pH. Neutron reflectometry was used to determine the... (More)
Multi-stimulus responsive poly(2-(2-methoxyethoxy)ethyl methacrylate-co-2-(diethylamino)ethyl methacrylate) [P(MEO2MA-co-DEA)] 80:20 mol % copolymer brushes were synthesized on planar silica substrates via surface-initiated activators continuously regenerated via electron transfer atom transfer radical polymerization. Brush thickness was sensitive to changes in pH and temperature as monitored with ellipsometry. At low pH, the brush is charged and swollen, while at high pH, the brush is uncharged and more collapsed. Clear thermoresponsive behavior is also observed with the brush more swollen at low temperatures compared to high temperatures at both high and low pH. Neutron reflectometry was used to determine the polymer volume fraction profiles (VFPs) at various pH values and temperatures. A region of lower polymer content, or a depletion region, near the substrate is present in all of the experimental polymer VFPs, and it is more pronounced at low pH (high charge) and less so at high pH (low charge). Polymer VFPs calculated through numerical self-consistent field theory suggest that enrichment of DEA monomers near the substrate results in the experimentally observed non-monotonic VFPs. Adsorption of DEA monomers to the substrate prior to initiation of polymerization could give rise to DEA segment-enriched region proximal to the substrate. (Less)
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author
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publishing date
type
Contribution to journal
publication status
published
subject
in
Langmuir
volume
36
issue
42
pages
13 pages
publisher
The American Chemical Society (ACS)
external identifiers
  • scopus:85094869903
ISSN
0743-7463
DOI
10.1021/acs.langmuir.0c01502
language
English
LU publication?
no
id
f3f47ae9-600e-48db-a00b-705a2f3f9408
date added to LUP
2022-04-01 21:03:06
date last changed
2022-06-04 04:18:43
@article{f3f47ae9-600e-48db-a00b-705a2f3f9408,
  abstract     = {{Multi-stimulus responsive poly(2-(2-methoxyethoxy)ethyl methacrylate-<i>co</i>-2-(diethylamino)ethyl methacrylate) [P(MEO<sub>2</sub>MA-<i>co</i>-DEA)] 80:20 mol % copolymer brushes were synthesized on planar silica substrates via surface-initiated activators continuously regenerated via electron transfer atom transfer radical polymerization. Brush thickness was sensitive to changes in pH and temperature as monitored with ellipsometry. At low pH, the brush is charged and swollen, while at high pH, the brush is uncharged and more collapsed. Clear thermoresponsive behavior is also observed with the brush more swollen at low temperatures compared to high temperatures at both high and low pH. Neutron reflectometry was used to determine the polymer volume fraction profiles (VFPs) at various pH values and temperatures. A region of lower polymer content, or a depletion region, near the substrate is present in all of the experimental polymer VFPs, and it is more pronounced at low pH (high charge) and less so at high pH (low charge). Polymer VFPs calculated through numerical self-consistent field theory suggest that enrichment of DEA monomers near the substrate results in the experimentally observed non-monotonic VFPs. Adsorption of DEA monomers to the substrate prior to initiation of polymerization could give rise to DEA segment-enriched region proximal to the substrate.}},
  author       = {{Johnson, Edwin C and Willott, Joshua D and Gresham, Isaac J and Murdoch, Timothy J and Humphreys, Ben A and Prescott, Stuart W and Nelson, Andrew and de Vos, Wiebe M and Webber, Grant B and Wanless, Erica J}},
  issn         = {{0743-7463}},
  language     = {{eng}},
  number       = {{42}},
  pages        = {{12460--12472}},
  publisher    = {{The American Chemical Society (ACS)}},
  series       = {{Langmuir}},
  title        = {{Enrichment of charged monomers explains non-monotonic polymer volume fraction profiles of multi-stimulus responsive copolymer brushes}},
  url          = {{http://dx.doi.org/10.1021/acs.langmuir.0c01502}},
  doi          = {{10.1021/acs.langmuir.0c01502}},
  volume       = {{36}},
  year         = {{2020}},
}