- Experimental investigation on dynamic wetting of soluble or deformable substrates
Experimental investigation on dynamic wetting of soluble or deformable substrates
Determine the effect of the deformation, swelling and dissolution of polystyrene substrates in a wetting solvent (toluene) on the wetting dynamics
Originality and innovative aspects: The wetting process of solids by liquids can be divided into two processes, a fast (controlled by inertial forces), and a slow (controlled by viscous forces). An empirical power law describes the dependence of the wetting speed on the surface wettability for simple liquids and surfaces. It is not yet known if this power law is applicable to complex systems as well, e.g. liquids and surfaces structured at various length scales. Examples of surfaces are soluble polymer surfaces with different molecular weight; examples of liquids are polymer solutions or dispersions. The proposed research will shed light on the process of spreading of a droplet of solvent on a soluble polymer surface. This droplet will turn into a polymer solution – due to solvation of polymer in the solvent during spreading – and thus continuously change its composition (concentration, viscosity, surface tension).
Methodologies: The fast and slow wetting will be studied with high speed imaging and with laser scanning confocal microscopy; droplet evaporation will be studied by analysis of the final drop imprints on the polymer surface. Radii of toluene droplets will vary between 50 and 500 µm. Polystyrene molecular weights will vary between 1 kDa (polymer melt) and 500 kDa (solid).
 L. Chen, G.K. Auernhammer, E. Bonaccurso, Soft Matter 7, 9084-9089 (2011).
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