Optical characterization of co-nonsolvency effects in thin responsive PNIPAAm-based gel layers exposed to ethanol/water mixtures

Reference:

Anac, I., Aulasevich, A., Junk, M. J. N., Jakubowicz, P., Roskamp, R. F., Menges, B., Jonas, U. and Knoll, W., 2010. Optical characterization of co-nonsolvency effects in thin responsive PNIPAAm-based gel layers exposed to ethanol/water mixtures. Macromolecular Chemistry and Physics, 211 (9), pp. 1018-1025.

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Official URL:

http://dx.doi.org/10.1002/macp.200900533

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 °Cin pure water to 29.7 °C with only 0.25 vol.-% etha- nol. Between 20 and 70% ethanol and >10 °C (the practical temperature limit) the layers existed only in the collapsed state. A reentrant Tc of 40.2 °C was found at 70% ethanol while at higher ethanol volume fraction no Tc could be recorded.

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