Crack Patterns in Thin Polymer Layers

Abstract

Summary: During the solidification of thin polymer layers different crack patterns can occur. There are several mechanisms of the development of regular crack defects and layer fractures. In case of self‐organization caused by Marangoni instability at the fluid layer surface the substrate can be periodically uncovered by spreading motions when dewetting hinders a back flow from the higher spots of the layer. Another type of crack patterns is generated from shrinkage processes and stress differences in the drying layer. Mostly these patterns are characterized by intersecting straight cracks. In this paper some examples of unusual shrinkage‐crack patterns in polymer layers are presented. Their propagation is independent on surface flow and surface deformations caused by the Marangoni effect, although the strength of polymer layers is impaired by the interfacial instability. Especially at layer edges or spots with thickness differences one can observe periodic wavy or circularly bend shrinkage‐crack structures. As a third type ramified surface defects are studied in thin layers. Often they only propagate at the layer surface.Wavy shrinkage‐cracks in a PMMA layer with longish surface elevations.imageWavy shrinkage‐cracks in a PMMA layer with longish surface elevations.

Self-assembly in evaporated polymer solutions: Influence of the solution concentration

“…Applications of micro-scaled relieves obtained under evaporation of polymer solutions as biomedical interfaces has been discussed intensively as well [4,5]. It was demonstrated that under particular conditions, intensive evaporation of the solution gives rise to ordered self-assembled patterns on a length scale significantly exceeding molecular dimensions [6][7][8][9][10][11][12][13][14]. Similar patterns were observed under evaporation of volatile liquids [15,16].…”

Mesoscopic Patterning in Thin Polymer Films Formed under the Fast Dip‐Coating Process

“…Weh and theoretically treated by De Gennes [2,15] . It seems that these structures have a potential as photonic molecules.…”

“…3) or centers (see Fig. 6) could be explained in the framework of the concept developed by Weh, who related the effect to the Marangoni instability, which induced spreading motions of the solution [2] . However, insensitivity of the mesoscopic cell size to the kind of polymer or used solvent calls for an explanation, which will be proposed below.…”

“…Micrometric (i.e., mesoscopic) polymer structures attracted considerable interest recently [1][2][3] . It was shown that processes of self-assembling and self-organization bring into existence strictly ordered, periodic mesoscopically scaled patterns, thus allowing various optical applications, including photonic molecules and full dielectric long period gratings (LPG) -a new class of dielectric media that can provide novel ways to manipulate and control light.…”

Free‐Standing, Thermostable, Micrometer‐Scale Honeycomb Polymer Films and their Properties

“…The origin of this pattern is not clear, and is related by many researchers to various kinds of interfacial instabilities: Marangoni (surface-tension-driven), evaporation or masstransport-driven ones. [23][24][25][33][34][35][36][37][38][39][40][41][42] The high dispersion of pore sizes seen in Figure 2 makes this pattern unsuitable for most of the applications mentioned above.…”