Silicone nanofilaments
Silicone nanofilaments have a diameter of approx. 5 nm and a length of a few micrometers. They are made from silanes . Chemically, they are structured like silicones , but due to their nanostructure they have completely different physical and chemical properties. They were developed in 2004 by the chemist Stefan Seeger and his research group at the University of Zurich . In the meantime, the great application potential has been shown in numerous scientific publications.
structure
The chemical structure of silicon nanofilaments corresponds to that of silicones , that is, silicon atoms are connected to one another via oxygen atoms. If more than two oxygen atoms act as bridging atoms , three-dimensional networks are formed. The fourth binding site of the silicon atoms is then saturated by an organic residue.
Under certain conditions, no massive silicon solids are formed on surfaces during the synthesis, but rather small filaments that are only a few nanometers thick and only a few tens of nanometers long. Why these structures arise has not yet been fully clarified.
Manufacturing
Silicone nanofilaments were initially produced from the gas phase in a time-consuming process. For this purpose, trichlorosilane was evaporated in a reaction chamber together with a precisely set humidity and a substrate was exposed to this mixture for several hours. It is important that the concentration of trichlorosilane and air humidity is set very precisely, otherwise the condensation reaction will take place, i.e. That is, the silicone forms, but no nanofilaments.
properties
Silicone nanofilaments have diverse, sometimes extreme properties, which can be turned into the extreme opposite through subsequent chemical modification. Surfaces coated with silicone nanofilaments are extremely water-repellent, they say, super hydrophobic . Drops of water lie on the surface as almost round spheres; there is practically no wetting. This property can be quantitatively described as the contact angle , which in the case of silicone nanofilament layers is approximately up to 170 °. If the surface is only at a small angle, e.g. B. 2 ° at an angle, the pearls roll off the surface immediately.
Silicone nanofilaments can also be chemically modified so that they can be used e.g. B. super hydrophilic , super lipophilic , super lipophobic or superhydrophobic and superlipophob be at the same time.
literature
- GRJ Artus, S. Jung, J. Zimmermann, H.-P. Gautschi, K. Marquardt, S. Seeger: Silicone Nanofilaments and Their Application as Superhydrophobic Coatings . In: Advanced Materials . tape 18 , no. 20 , September 20, 2006, pp. 2758-2762 , doi : 10.1002 / adma.200502030 .
Individual evidence
- ↑ patent WO2004113456 : coating Superhydrophobic. Published on December 29, 2004 , inventors: J. Zimmermann, S. Seeger, G. Artus, S. Jung.