Probing the thermal collapse of poly(N-isopropylacrylamide) grafts by quantitative in situ ellipsometry

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Abstract

We demonstrate the potential of in situ spectroscopic ellipsometry for the investigation of the chain segment density profile and layer thickness during the temperature-induced, reversible collapse–expansion transition of poly(N-isopropylacrylamide) (PNIPAM) grafted layers. Here, we study PNIPAM films with variable grafting densities in aqueous systems, which were produced by atom-transfer radical polymerization (ATRP). In our attempt to obtain a realistic quantitative description of the thickness of our swollen PNIPAM layers, various models were implemented to fit the ellipsometric data. As expected, we found that the swelling ratio is strongly dependent on the grafting density. From the ellipsometry results, the density and thickness variation accompanying the collapse transition across the lower critical solution temperature (LCST) was characterized. The collapse can be adequately explained by considering the PNIPAM film to consist of two layers: (i) a dense layer near the surface and (ii) a more diluted layer on the side of the film exposed to the solvent. Analysis of the optical response reveals a gradient density profile within these layers
Original languageEnglish
Pages (from-to)9261-9268
Number of pages8
JournalJournal of physical chemistry B
Volume116
Issue number30
DOIs
Publication statusPublished - 2012

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Ellipsometry
Grafts
ellipsometry
Spectroscopic ellipsometry
Atom transfer radical polymerization
Swelling
Temperature
profiles
Hot Temperature
poly-N-isopropylacrylamide
swelling
polymerization
gradients
temperature
atoms

Keywords

  • IR-81169
  • METIS-287552

Cite this

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title = "Probing the thermal collapse of poly(N-isopropylacrylamide) grafts by quantitative in situ ellipsometry",
abstract = "We demonstrate the potential of in situ spectroscopic ellipsometry for the investigation of the chain segment density profile and layer thickness during the temperature-induced, reversible collapse–expansion transition of poly(N-isopropylacrylamide) (PNIPAM) grafted layers. Here, we study PNIPAM films with variable grafting densities in aqueous systems, which were produced by atom-transfer radical polymerization (ATRP). In our attempt to obtain a realistic quantitative description of the thickness of our swollen PNIPAM layers, various models were implemented to fit the ellipsometric data. As expected, we found that the swelling ratio is strongly dependent on the grafting density. From the ellipsometry results, the density and thickness variation accompanying the collapse transition across the lower critical solution temperature (LCST) was characterized. The collapse can be adequately explained by considering the PNIPAM film to consist of two layers: (i) a dense layer near the surface and (ii) a more diluted layer on the side of the film exposed to the solvent. Analysis of the optical response reveals a gradient density profile within these layers",
keywords = "IR-81169, METIS-287552",
author = "Kooij, {Ernst S.} and Xiaofeng Sui and Hempenius, {Mark A.} and Zandvliet, {Henricus J.W.} and Vancso, {Gyula J.}",
year = "2012",
doi = "10.1021/jp304364m",
language = "English",
volume = "116",
pages = "9261--9268",
journal = "Journal of physical chemistry B",
issn = "1520-6106",
publisher = "American Chemical Society",
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TY - JOUR

T1 - Probing the thermal collapse of poly(N-isopropylacrylamide) grafts by quantitative in situ ellipsometry

AU - Kooij, Ernst S.

AU - Sui, Xiaofeng

AU - Hempenius, Mark A.

AU - Zandvliet, Henricus J.W.

AU - Vancso, Gyula J.

PY - 2012

Y1 - 2012

N2 - We demonstrate the potential of in situ spectroscopic ellipsometry for the investigation of the chain segment density profile and layer thickness during the temperature-induced, reversible collapse–expansion transition of poly(N-isopropylacrylamide) (PNIPAM) grafted layers. Here, we study PNIPAM films with variable grafting densities in aqueous systems, which were produced by atom-transfer radical polymerization (ATRP). In our attempt to obtain a realistic quantitative description of the thickness of our swollen PNIPAM layers, various models were implemented to fit the ellipsometric data. As expected, we found that the swelling ratio is strongly dependent on the grafting density. From the ellipsometry results, the density and thickness variation accompanying the collapse transition across the lower critical solution temperature (LCST) was characterized. The collapse can be adequately explained by considering the PNIPAM film to consist of two layers: (i) a dense layer near the surface and (ii) a more diluted layer on the side of the film exposed to the solvent. Analysis of the optical response reveals a gradient density profile within these layers

AB - We demonstrate the potential of in situ spectroscopic ellipsometry for the investigation of the chain segment density profile and layer thickness during the temperature-induced, reversible collapse–expansion transition of poly(N-isopropylacrylamide) (PNIPAM) grafted layers. Here, we study PNIPAM films with variable grafting densities in aqueous systems, which were produced by atom-transfer radical polymerization (ATRP). In our attempt to obtain a realistic quantitative description of the thickness of our swollen PNIPAM layers, various models were implemented to fit the ellipsometric data. As expected, we found that the swelling ratio is strongly dependent on the grafting density. From the ellipsometry results, the density and thickness variation accompanying the collapse transition across the lower critical solution temperature (LCST) was characterized. The collapse can be adequately explained by considering the PNIPAM film to consist of two layers: (i) a dense layer near the surface and (ii) a more diluted layer on the side of the film exposed to the solvent. Analysis of the optical response reveals a gradient density profile within these layers

KW - IR-81169

KW - METIS-287552

U2 - 10.1021/jp304364m

DO - 10.1021/jp304364m

M3 - Article

VL - 116

SP - 9261

EP - 9268

JO - Journal of physical chemistry B

JF - Journal of physical chemistry B

SN - 1520-6106

IS - 30

ER -