Supporting Information Photoswitchable Ratchet Surface Topographies based on Self-Protonating Spiropyran-NIPAAM Hydrogels Jelle E. Stumpel, Bartosz Ziółkowski, Larisa Florea, Dermot Diamond,,, Dirk J. Broer *,, *, and Albertus P. H. J. Schenning Department of Functional Organic Materials and Devices, Chemical Engineering and Chemistry, Eindhoven University of Technology. Den Dolech, 56 AZ Eindhoven, The Netherlands. E-mail: d.broer@tue.nl; a.p.h.j.schenning@tue.nl The INSIGHT Centre for Data Analytics, National Centre for Sensor Research, School of Chemical Sciences, Dublin City University, Glasnevin, Dublin 9, Ireland. Institute for Complex Molecular Systems and Laboratory of Macromolecular and Organic Chemistry, Eindhoven University of Technology, P.O. Box 53, 56 MB, Eindhoven, The Netherlands
. Initial Polymerized Absorbance (a.u.). 6 8 Wavenumber (cm - ) Figure S. FT-IR spectrum before and after polymerization of the monomer mixture. After polymerization, signals at 986, 956 and 88 cm -, related to the polymerizable acrylamide group, have disappeared. Figure S. Optical images of a constrained hydrogel (mixture ) before and after swelling in demineralised water.
. Mixture Mixture Absorbance (normalised). 5 5 Time (min) Figure S3. Reversible photoresponsive behaviour of the constrained hydrogel polymer films. The change of the absorption intensity at 7 nm is depicted during four successive exposure steps for hydrogels prepared from mixture and.. MBIS TPGDA Absorbance (normalised). 5 5 Time (min) Figure S. Comparison of back-isomerisation between MBIS and TPGDA cross-linker hydrogel films. The absorption intensity at 7 nm is depicted during four successive exposure steps. 3
a) b). Absorbance (normalised). 5 5 5 Time (min) Figure S5. Reversible photoresponsive behaviour of hydrogel film containing a directly linked spiropyran unit as reported earlier. The absorption intensity at 3 nm is depicted during three successive exposure steps. Figure S6. Surface topographies of a surface constrained hydrogel film prepared from mixture before and after masked exposure (a, black area is the glass substrate which is set as zero) and the related cross section, as observed by interferometry.
a).5.5.5 mm.5.5.5 mm µm 8 6 Masked light exposure 8.. 6...6.6.8.8 mm mm b) - - -3 - -5 5 5 Figure S7. Surface topographies of a surface constrained hydrogel film prepared from mixture before and after masked exposure (a, black area is the glass substrate which is set as zero) and the related cross section (b), as observed by interferometry. Masked UV-exposure Flood UV-exposure Removal of the mask Homogeneous crosslink density High crosslink density Low crosslink density Figure S8. Schematic representation of the polymerization-induced diffusion process. During the first masked exposure step, more reactive diacrylate migrates towards the exposed area. A subsequent flood exposure step ensures full polymerization. 5
Figure S9. 3D height profiles of a hydrogel prepared by polymerisation-induced diffusion in the dry state (a), swollen (b) and after white light exposure (c), as observed by interferometry (lowest point in topographies is set as zero). 6
a) 3 6 8 b) 35 3 Swollen film Exposed film 5 5 5 3 5 Figure S. Cross sections of a coating prepared by polymerisation-induced diffusion after evaporation of dioxane (a) and the swollen film before and after white light exposure, as observed by interferometry (note: due to smoothing software, the topographies are presented more block-like than their actual shape, however, the minima and maxima were measured accurately). 7
Figure S. (a) Preparation method of surface topographies by pre-structured substrates and b) working principle of the ratchet-type of topography in water TPGDA ratchet template mixture ratchet (dry) mixture ratchet (dry) 5 5 5 5 Figure S. Cross section of the ratchet structures (TPGDA-copy and dry ratchets from mixture and, the slope is an average over 3 measurements), as observed by interferometry. 8
a) b) 8 6 6 8 8 6 6 8 Figure S3. Cross section of a ratchet prepared from mixture (containing mol% MBIS) before (a) and after (b) light exposure, as observed by interferometry. a) b) 5 3 6 8 5 3 6 8 Figure S. Cross section of a ratchet prepared from mixture (containing mol% MBIS) before (a) and after (b) light exposure, as observed by interferometry. 9
Figure S5. 3D height profiles of a ratchet prepared from mixture before (a) and after 5 (b), (c) and 5 (d) minutes of white light exposure, as observed by interferometry. () Ziółkowski, B.; Florea, L.; Theobald, J.; Benito-Lopez, F.; Diamond, D. Self- Protonating Spiropyran-Co-Nipam-Co-Acrylic Acid Hydrogel Photoactuators. Soft Matter 3, 9, 875-876.
() Stumpel, J. E.; Liu, D.; Broer, D. J.; Schenning, A. P. H. J. Photoswitchable Hydrogel Surface Topographies by Polymerisation-Induced Diffusion. Chem. - Eur. J. 3, 9, 9-97.