In situ atomic force microscopy studies of reversible light-induced switching of surface roughness and adhesion in azobenzene-containing PMMA films |
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Authors: | M MüllerY Gonzalez-Garcia C PakulaV Zaporojtchenko T StrunskusF Faupel R HergesD Zargarani OM Magnussen |
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Institution: | a Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität zu Kiel, Leibnizstr. 19, 24118 Kiel, Germany b Otto-Diels-Institut für Organische Chemie, Christian-Albrechts-Universität zu Kiel, Otto-Hahn-Platz 3, 24098 Kiel, Germany c Technische Fakultät der Christian-Albrechts-Universität zu Kiel, Kaiserstr. 2, 24143 Kiel, Germany |
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Abstract: | Thin films in the range 40-80 nm of a blend of PMMA with an azobenzene derivative have been studied directly during UV and blue light irradiation by atomic force microscopy (AFM), revealing highly reversible changes in the surface roughness and the film adhesion. UV light induces an ≈80% increase in surface roughness, whereas illumination by blue light completely reverses these changes. Based on the observed surface topography and transition kinetics a reversible mass flow mechanisms is suggested, where the polarity changes upon switching trigger a wetting-dewetting transition in a surface segregation layer of the chromophore. Similar AFM measurements of the pull-off force indicate a decrease upon UV and an increase after blue light illumination with a complex kinetic behavior: a rapid initial change, attributed to the change in the cis isomer fraction of the azobenzene derivative, and a more gradual change, indicative of slow structural reorganization. |
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Keywords: | Azobenzene PMMA Photoswitching Atomic force microscopy |
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