Zusammenhang zwischen lokaler molekularer Ordnung an Grenzflächen und deren Benetzungsverhalten

• Applicant: Privatdozent Dr. Hans Riegler
• Subject Area: Theoretical Condensed Matter Physics
• Term: from 1998 to 2003
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 5107238

The general aim of this proposal is a better understanding of the causes and effects of short range interactions in the context of wetting. For this purpose we shall investigate the relations between the wetting behaviour and the molecular ordering of the surface. As already described in the first proposal we intend to investigate the wetting behaviour of solid surfaces (silicon wafers) which are coated with molecularly thin layers of aliphatic molecules. Because of positive first results we will focus on molecularly thin layers of alskanes. Alkanes of certain chain lengths (16 to 50 C-atoms) automatically form monolayers on oxidized silicon surfaces due to surface freezing. These monolayers seem much better defined in their molecular order and they can be modified more systematically (e.g. the thickness via the chainlength, molecular roughness via mixtures) than alternative layers (LB-films, SAMs). As wetting liquids we will also use alkanes because they show an interesting and diverse wetting behaviour on surfaces covered with alkane monolayers. Another advantage of alkanes is their simple molecular structure. Thus they are suitable model substances to investigate general aspects of wetting and interfacial forces. As an extension to the original proposal we intend further to investigate the wetting behaviour of liquid surfaces which are covered with a Langmuir monolayer. The configuration of a water subphase which is covered with a Langmuir monolayer is especially well suited to individually investigate the short and the long range interaction components. The parameters which dominate the short and long range forces (e.g. monolayer packing and thickness vs subphase density) can be modified continuously and more individually than in configurations with solid surfaces. Again alkanes shall be the wetting fluids.

• DFG Programme: Priority Programmes
• Subproject of: SPP 1052: Benetzung und Strukturbildung an Grenzflächen