Regensburg 2022 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 7: Wetting, Fluidics and Liquids at Interfaces and Surfaces

CPP 7.2: Vortrag

Montag, 5. September 2022, 11:00–11:15, H39

Liquid phase separation during soft dynamic wetting — •Lukas Hauer¹, Zhuoyun Cai², Jonathan T. Pham², and Doris Vollmer¹ — ¹Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany — ²Department of Chemical and Materials Engineering, University of Kentucky,Lexington, Kentucky, USA

Droplets sitting on soft substrates deform the material around the three-phase contact line, i.e., the formation of the wetting ridge. While on liquid films the ridge geometry is solely governed by capillarity, on (visco)elastic films elastic contributions add to the ridge geometry. Recently, on (visco)elastic materials a capillary induced phase-separated region of pure liquid was observed. Here, we investigate this phase separation on crosslinked PDMS films with differing amounts of free oligomer chains during dynamic wetting. We let droplets forcefully slide over PDMS films while monitoring the ridge zone with laser scanning confocal microscopy. Different dyes in the crosslinked network and in the free oligomers enable discrimination between the two phases. We find that phase-separation competes with the motion of the droplet: by tuning the droplets’ speed, the phase-separated ridge height ranges from >30 µm (at 5 µm/s) to no phase separation at all for fast speeds.