Optical Characterization of Co-Nonsolvency Effects in Thin Responsive PNIPAAm-Based Gel Layers Exposed to Ethanol/Water Mixtures
✍ Scribed by Ilke Anac; Alena Aulasevich; Matthias J. N. Junk; Piotr Jakubowicz; Robert F. Roskamp; Bernhard Menges; Ulrich Jonas; Wolfgang Knoll
- Publisher
- John Wiley and Sons
- Year
- 2010
- Tongue
- English
- Weight
- 438 KB
- Volume
- 211
- Category
- Article
- ISSN
- 1022-1352
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✦ Synopsis
Abstract
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.
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