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Optical Characterization of Co‐Nonsolvency Effects in Thin Responsive PNIPAAm‐Based Gel Layers Exposed to Ethanol/Water Mixtures
Author(s) -
Anac Ilke,
Aulasevich Alena,
Junk Matthias J. N.,
Jakubowicz Piotr,
Roskamp Robert F.,
Menges Bernhard,
Jonas Ulrich,
Knoll Wolfgang
Publication year - 2010
Publication title -
macromolecular chemistry and physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.57
H-Index - 112
eISSN - 1521-3935
pISSN - 1022-1352
DOI - 10.1002/macp.200900533
Subject(s) - ethanol , solvent , thin film , chemistry , surface plasmon resonance , poly(n isopropylacrylamide) , spectroscopy , copolymer , solvent effects , analytical chemistry (journal) , polymer chemistry , chemical engineering , materials science , chromatography , nanoparticle , organic chemistry , nanotechnology , polymer , engineering , physics , quantum mechanics
Surface‐attached, photo‐crosslinked gel films of a N ‐isopropylacrylamide copolymer were investigated in ethanol/water mixtures using a combination of surface plasmon resonance/optical waveguide spectroscopy with reversed WKB analysis. The solvent quality of the pure good solvents drops in their mixture and this co‐nonsolvency effect shifts the transition temperature ( T c ) in the µm‐thin gel films from 32.8 °C in pure water to 29.7 °C with only 0.25 vol.‐% ethanol. Between 20 and 70% ethanol and >10 °C (the practical temperature limit) the layers existed only in the collapsed state. A reentrant T c of 40.2 °C was found at 70% ethanol while at higher ethanol volume fraction no T c could be recorded.