Hydration and Solvent Exchange Induced Swelling and Deswelling of Homogeneous Poly(N-isopropylacrylamide) Microgel Thin Films
| Autor: | Tobias Widmann, Kun Wang, Nuri Hohn, Andreas J. Schmid, Jean-François Moulin, Yvonne Hannappel, Peter Müller-Buschbaum, Matthias Kühnhammer, Thomas Hellweg, Oliver Wrede, Lorenz Bießmann, Lucas P. Kreuzer, Stephan Rinner, Regine von Klitzing |
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| Rok vydání: | 2019 |
| Předmět: |
Materials science
Kinetics 02 engineering and technology Surfaces and Interfaces 010402 general chemistry 021001 nanoscience & nanotechnology Condensed Matter Physics 01 natural sciences Polyelectrolyte 0104 chemical sciences chemistry.chemical_compound Colloid chemistry Chemical engineering Electrochemistry Poly(N-isopropylacrylamide) General Materials Science Neutron reflectometry Thin film Fourier transform infrared spectroscopy 0210 nano-technology Spectroscopy |
| Zdroj: | Langmuir. 35:16341-16352 |
| ISSN: | 1520-5827 0743-7463 |
| DOI: | 10.1021/acs.langmuir.9b03104 |
| Popis: | The investigation of the response kinetics of smart colloidal microgel films is crucial for their optimization to enable advanced applications. We study the classical thermoresponsive microgel model system N-isopropylacrylamide cross-linked with N,N'-methylenebisacrylamide. Without the typically used polyelectrolyte coating of the substrate, thin microgel films are prepared in a single spin-coating step. Atomic force microscopy measurements reveal an extremely dense packing, resulting in a homogeneous compact thin film of microgel particles. The hydration kinetics of these films in H2O and D2O atmospheres as well as the kinetics of the solvent exchange between both water species are investigated with in situ time-of-flight neutron reflectometry (TOF-NR) and in situ Fourier-transform infrared (FTIR) spectroscopy. With accounting for a nonconstant humid atmosphere, the intrinsic diffusion dynamics of water molecules into the thin microgel film are modeled and the specific time constant tau and the effective Flory-Huggins interaction parameter chi(eff) are determined. Comparing the results in H2O and D2O atmospheres, TOF-NR and FTIR spectroscopy results show an increased affinity of the microgel films toward H2O as compared to D2O. From the FTIR spectroscopy data, we further identify different kinetics of intermolecular processes and order them according to their temporal evolution. |
| Databáze: | OpenAIRE |
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