%0 Generic
%A Mielke, Salomé
%D 2019
%F heidok:26715
%R 10.11588/heidok.00026715
%T Interfacial Viscoelasticity and Structure of Self-Assembled Semifluorinated Alkanes on Water
%U https://archiv.ub.uni-heidelberg.de/volltextserver/26715/
%X Semifluorinated alkanes self-assemble spontaneously into uniform nanometer-sized domains on water. The order of such “surface micelles” at the air/water interface is achieved by the counter balance of attractive and repulsive interactions. In this thesis, the viscoelastic properties of semifluorinated alkane monolayers are investigated by using interfacial shear and dilational rheology under oscillatory strain. The obtained response function implies a predominantly elastic character of the monolayers, suggesting repulsive interactions between the surface micelles. Both the structure and the form factor of the surface micelles are determined by the quantitative analysis of grazing-incidence small-angle X-ray scattering data. A systematic variation of the length and of the number of fluorocarbon and hydrocarbon chains unravel how a subtle change in the molecular structure modulates the size, shape and correlation of the surface micelles. A promising application of semifluorinated alkanes are contrast agent microbubbles for sonographic imaging. This thesis further shows that perfluorohexane vapor - commonly used to increase the lifetime of microbubbles - reduces the elasticity of the monolayers from semifluorinated alkanes whereas their structure is not influenced. The obtained results contribute to the fundamental understanding of the formation and mechanics of mesoscopic molecular assembly at the interface.