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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 44: Wetting, Fluidics and Liquids at Interfaces and Surfaces II (joint session CPP/DY)
CPP 44.5: Talk
Thursday, March 30, 2023, 10:30–10:45, MER 02
Demixing of liquid PDMS during dewetting into the equilibrium state — •Khalil Remini1, Leonie Schmeller2, Dirk Peschka2, Barbara Wagner2, and Ralf Seemann1 — 1Experimental Physics, Saarland University, Saarbrücken, Germany — 2Weierstrass-Institute, Berlin University, Berlin, Germany
The study of micrometer-sized equilibrium droplets on elastic substrates is of great interest because, due to negligible gravity, other interactions such as elastic or capillary forces and their mutual influence can easily be investigated, so deviations from the expected behaviour at larger scales becomes visible. This applies in particular to soft solids like PDMS that are typically considered as ideal rubbers on the macro scale. Our experimental system is composed of liquid polystyrene (PS) droplets on a viscoelastic substrate consisting of cross-linked polydimethylsiloxane (PDMS) of different elasticities. Using atomic force microscopy (AFM), we analyse the topography of the materials and thus their contact angles with high precision, we also use AFM to demonstrate the existence of non-cross-linked liquid PDMS that migrates from the elastic PDMS toward the three-phase contact line TPCL to form a demixed liquid ring around the dewetted PS droplet. In that situation, on the nanometer distance around the TPCL, liquid PS meets liquid PDMS instead of being in direct contact with the soft solid PDMS. Further analysis allows us to say that this phenomenon also exists during the dewetting of liquid polystyrene in the same type of elastic solids.