Self-organized formation of low-dimensional network structures starting from a nitrocellulose solution

Full Paper: Low-dimensional solid state structures in the form of a hexagon al network are particularly interesting far unveiling new physical properti es of condensed matter and, moreover, due to their properties as photonic c rystals. Besides the so far well-established structuring with advanced lith ographic methods, it is also possible to take advantage of self-organizatio n processes for the gain of those low-dimensional structures. In the follow ing paper, we introduce an experimental method that is capable of producing highly regular polymer network patterns on the basis of different cell typ es. The diameter of a hexagonal cell amounts to 1.5-2.0 mum. Our method is based on the wetting of a drop of the polymer solution (nitrocellulose in a myl acetate) on the surface of distilled water cooled down to a temperature of 3 to 5 degreesC and the influence of the water vapor on the created pol ymer thin film. Following the self-organized process of precipitating water vapor drops on the polymer layer, pulling the latter to the water drop, an d subsequently evaporating the solvent, we end up with a structuring of the polymer thin film to a hexagonal network. Depending on the time elapsed af ter the water vapor has begun to affect the polymer layer, one obtains diff erent forms of net structures. The size of the hexagonal cells results from the extension of the water vapor drop. We propose a structuring model capa ble of explaining the morphology of the individual cells inside the network obtained in the experiment. [GRAPHICS] Model for the lay on of the water steam on the polymer layer: (a) Water dro ps before their contact with the surface of the polymer layer. (b) Moment o f first contact with the polymer layer. (c) Process of envelopment of the w ater drop by the polymer layer (dashed lines between the water drops indica te the profile of neighboring water drops). (d) Moment of the first contact of the water drop with the cooled water surface (dashed lines between the water drops indicate the profile of neighboring water drops). The thin film on the surface of the water drop indicates a monomolecular polymer layer.