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Evolution Of Fractal-like Surface Structures In Layers Of Polyacrylonitrile Solutions By Interfacial Dynamic Processes.
Published 2004 · Chemistry, Medicine
Solvent evaporation causes concentration and temperature gradients at the free surface of a coating polymer solution. Thereby surface-tension-driven flows can result in a surface instability with regular structures within the layer. Different types of surface structures can occur at spots with thickness differences. One can find fractal-like structures especially in the edge zone of a layer. The evolution of such fractal-like structures at the surfaces of coating solutions of polyacrylonitrile (PAN) in dimethylformamide (DMF) during layer hardening is examined. Condensation of water on the surface of the fluid layer exerts a strong influence on the formation of these structures. Solutions of PAN in DMF are important for the production of ultrafiltration membranes. Such membranes are produced by precipitation in a water bath after a short open time.