Microstructures by solvent drop evaporation on polymer surfaces: dependence on molar mass |
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Authors: | Li Guangfen Butt Hans-Jürgen Graf Karlheinz |
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Affiliation: | Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany. |
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Abstract: | When a solvent drop evaporates from a polymer surface, it leaves behind a characteristic structure, typically a crater. We deposited toluene drops with a microsyringe onto planar polystyrene (PS) surfaces and analyzed the surface topography after drying. For low molar mass PS (Mw = 20.9-24.3 kDa) dotlike protrusions with a ridge at the periphery formed on the polymer surface. With increasing molar mass the central region decreased in height. At Mw = 29.6-643 kDa a craterlike structure with a depression in the center and a ridge was observed. At even higher molar mass, irregular structures without rotational symmetry occurred. We explain the observed dependence on the molar mass with a different degree of entanglement, leading to different dissolution rates and different diffusion constants. |
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