Analysis of optical gradient profiles during temperature- and salt-dependent swelling of thin responsive hydrogel films

M J N Junk, I Anac, Bernhard Menges, U Jonas

Research output: Contribution to journalArticle

  • 27 Citations

Abstract

Surface-attached, cross-linked hydrogel films based on thermoresponsive N-isopropylacrylamide with a dry thickness > 1 mu m were studied with surface plasmon resonance/optical waveguide mode spectroscopy (SPR/OWS) to monitor temperature-dependent and salt-induced changes of their swelling state. In combination with the reversed Wentzel-Kramers-Brillouin and Bruggeman effective medium approximation and by modeling the hydrogel film as a composite of sublayers with individual complex refractive indices, refractive index/volume fraction gradient profiles perpendicular to the surface are accessible simultaneously with information about local inhomogeneities. Specifically, the imaginary refractive index kappa of each sublayer can be interpreted as a measure for static and dynamic inhomogeneities, which were found to be highest at the volume transition collapse temperature in the layer center. These results indicate that the hydrogel collapse originates rather from the film center than from its boundaries. Upon addition of NaCl to a swollen hydrogel below its transition temperature, comparable optical loss characteristics as for the thermal gel collapse arc observed with respect to inhomogeneities. Interestingly, in contrast to the thermally induced layer shrinkage and collapse, swelling increases at intermediate salt concentrations.
LanguageEnglish
Pages12253-12259
Number of pages7
JournalLangmuir
Volume26
Issue number14
DOIs
StatusPublished - 20 Jul 2010

Fingerprint

Hydrogels
swelling
temperature profiles
Swelling
Refractive index
Salts
Hydrogel
salts
gradients
inhomogeneity
refractivity
Superconducting transition temperature
Optical losses
Surface plasmon resonance
Optical waveguides
Temperature
Volume fraction
Gels
surface plasmon resonance
shrinkage

Cite this

Analysis of optical gradient profiles during temperature- and salt-dependent swelling of thin responsive hydrogel films. / Junk, M J N; Anac, I; Menges, Bernhard; Jonas, U.

In: Langmuir, Vol. 26, No. 14, 20.07.2010, p. 12253-12259.

Research output: Contribution to journalArticle

Junk, M J N ; Anac, I ; Menges, Bernhard ; Jonas, U. / Analysis of optical gradient profiles during temperature- and salt-dependent swelling of thin responsive hydrogel films. In: Langmuir. 2010 ; Vol. 26, No. 14. pp. 12253-12259
@article{7dece18a241a4731950c9fcbd9222ba4,
title = "Analysis of optical gradient profiles during temperature- and salt-dependent swelling of thin responsive hydrogel films",
abstract = "Surface-attached, cross-linked hydrogel films based on thermoresponsive N-isopropylacrylamide with a dry thickness > 1 mu m were studied with surface plasmon resonance/optical waveguide mode spectroscopy (SPR/OWS) to monitor temperature-dependent and salt-induced changes of their swelling state. In combination with the reversed Wentzel-Kramers-Brillouin and Bruggeman effective medium approximation and by modeling the hydrogel film as a composite of sublayers with individual complex refractive indices, refractive index/volume fraction gradient profiles perpendicular to the surface are accessible simultaneously with information about local inhomogeneities. Specifically, the imaginary refractive index kappa of each sublayer can be interpreted as a measure for static and dynamic inhomogeneities, which were found to be highest at the volume transition collapse temperature in the layer center. These results indicate that the hydrogel collapse originates rather from the film center than from its boundaries. Upon addition of NaCl to a swollen hydrogel below its transition temperature, comparable optical loss characteristics as for the thermal gel collapse arc observed with respect to inhomogeneities. Interestingly, in contrast to the thermally induced layer shrinkage and collapse, swelling increases at intermediate salt concentrations.",
author = "Junk, {M J N} and I Anac and Bernhard Menges and U Jonas",
year = "2010",
month = "7",
day = "20",
doi = "10.1021/la101185q",
language = "English",
volume = "26",
pages = "12253--12259",
journal = "Langmuir",
issn = "0743-7463",
publisher = "American Chemical Society",
number = "14",

}

TY - JOUR

T1 - Analysis of optical gradient profiles during temperature- and salt-dependent swelling of thin responsive hydrogel films

AU - Junk,M J N

AU - Anac,I

AU - Menges,Bernhard

AU - Jonas,U

PY - 2010/7/20

Y1 - 2010/7/20

N2 - Surface-attached, cross-linked hydrogel films based on thermoresponsive N-isopropylacrylamide with a dry thickness > 1 mu m were studied with surface plasmon resonance/optical waveguide mode spectroscopy (SPR/OWS) to monitor temperature-dependent and salt-induced changes of their swelling state. In combination with the reversed Wentzel-Kramers-Brillouin and Bruggeman effective medium approximation and by modeling the hydrogel film as a composite of sublayers with individual complex refractive indices, refractive index/volume fraction gradient profiles perpendicular to the surface are accessible simultaneously with information about local inhomogeneities. Specifically, the imaginary refractive index kappa of each sublayer can be interpreted as a measure for static and dynamic inhomogeneities, which were found to be highest at the volume transition collapse temperature in the layer center. These results indicate that the hydrogel collapse originates rather from the film center than from its boundaries. Upon addition of NaCl to a swollen hydrogel below its transition temperature, comparable optical loss characteristics as for the thermal gel collapse arc observed with respect to inhomogeneities. Interestingly, in contrast to the thermally induced layer shrinkage and collapse, swelling increases at intermediate salt concentrations.

AB - Surface-attached, cross-linked hydrogel films based on thermoresponsive N-isopropylacrylamide with a dry thickness > 1 mu m were studied with surface plasmon resonance/optical waveguide mode spectroscopy (SPR/OWS) to monitor temperature-dependent and salt-induced changes of their swelling state. In combination with the reversed Wentzel-Kramers-Brillouin and Bruggeman effective medium approximation and by modeling the hydrogel film as a composite of sublayers with individual complex refractive indices, refractive index/volume fraction gradient profiles perpendicular to the surface are accessible simultaneously with information about local inhomogeneities. Specifically, the imaginary refractive index kappa of each sublayer can be interpreted as a measure for static and dynamic inhomogeneities, which were found to be highest at the volume transition collapse temperature in the layer center. These results indicate that the hydrogel collapse originates rather from the film center than from its boundaries. Upon addition of NaCl to a swollen hydrogel below its transition temperature, comparable optical loss characteristics as for the thermal gel collapse arc observed with respect to inhomogeneities. Interestingly, in contrast to the thermally induced layer shrinkage and collapse, swelling increases at intermediate salt concentrations.

UR - http://www.scopus.com/inward/record.url?scp=77956712804&partnerID=8YFLogxK

UR - http://dx.doi.org/10.1021/la101185q

U2 - 10.1021/la101185q

DO - 10.1021/la101185q

M3 - Article

VL - 26

SP - 12253

EP - 12259

JO - Langmuir

T2 - Langmuir

JF - Langmuir

SN - 0743-7463

IS - 14

ER -