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Abstract:
Flow processes on the micro- and nanometer scale are of enormous scientific interest and additionally hold, e.g. in lab-on-a-chip applications, large technological potential. The under-standing of the stability and the dynamics of thin liquid films allows for drawing conclusions about the interactions at interfaces and on the behavior of liquids on the molecular level.
Thin polymer films on hydrophobic substrates are subject to different dewetting mechanisms such as e.g. the nucleation of holes. The focus of this study lies in particular on the quantification of the hydrodynamic boundary condition at the solid/liquid interface, the slip length.
In the first part, the dynamics of hole growth was studied. Thereby, the impact of the substrate on the dewetting dynamics is quantified. Moreover, it is found that the length of the polymer chains exerts a dominating influence on the slip length and, thus, on the flow properties. In the
second part of this thesis, the morphology of the rim surrounding the hole is studied. Based on theoretical models, the slip length characterizing the boundary condition is determined. It is shown that the slip length scales with the third power of the chain length of the polymer as soon as chain entanglements occur. At the interface itself, the density of entanglements is reduced by a factor of 3 to 4. These findings emphasize the relevance of polymer conformations
at the solid/liquid interface for the flow properties.
