This study is devoted to the experimental and theoretical investigation of aerodynamic drop breakup phenomena. We show that the phenomena of drop impact onto a rigid wall, drop binary collisions, and aerodynamic drop deformation are similar if the correct scaling is applied. Then we use observations of the deforming drop to estimate the evolution of the film thickness of the bag, the value that determines the size of the fine child drops produced by bag breakup. This prediction of film thickness, based on film kinematics, is validated for the initial stage by direct drop thickness measurements and at the latest stage by the data obtained from the velocity of hole expansion in the film. It is shown that the film thickness correlates well with the dimensionless position of the bag apex.

Elastic properties of surfactant membranes can be described in terms of the bending rigidity k and the saddle splay modulus k. Phase diagram measurements and neutron scattering experiments allowed the determination of these parameters. Recent simulations showed that the bending rigidity, which is deduced from the characteristic length scales in the microemulsion, is a mixture of k and k. By combining neutron spin echo (NSE) spectroscopy, small angle neutron scattering (SANS) and phase diagram measurements, we show that also experimentally the different contributions can be separated.For supercritical CO 2 microemulsions and bicontinuous microemulsions with additives, the prefactors of the k and k contributions are determined and compared to those from simulations.

Microemulsions of the type H(2)O-scCO(2)-surfactant are potential candidates for novel solvent mixtures in the field of green chemistry. Furthermore, scCO(2)-microemulsions are highly interesting from a fundamental point of view since their properties such as the bending elastic constants can be strongly influenced solely by varying the pressure without changing the components. With this motivation we studied the phase behavior and the microstructure of water-rich scCO(2)-microemulsions. Such microemulsions were formulated using the technical grade non-ionic surfactants Zonyl FSO 100 and Zonyl FSN 100. At elevated pressures the temperature dependent phase behavior of these systems follows the general patterns of non-ionic microemulsions. Small angle neutron scattering experiments were conducted to determine the length scales and the topology of the microstructure of these systems. Having determined the exact scattering length densities and the composition of the respective sub-phases by a systematic contrast variation we could show that these systems consist of CO(2)-swollen microemulsion droplets that are dispersed in a continuous aqueous-phase. The scattering data were analyzed using a newly derived form factor for polydisperse, spherical core/shell particles with diffuse interfaces. The underlying analytical density profiles could be confirmed applying the model-free Generalized Indirect Fourier Transformation (GIFT) to the scattering data. Following the general patterns of non-ionic microemulsions the radius of the microemulsion droplets is found to increase almost linearly upon the addition of CO(2).

The bending rigidity of surfactant membranes in novel bicontinuous CO 2 -microemulsions of the type H 2 O/NaCl-scCO 2 -Zonyl FSH/Zonyl FSN 100 was determined using both high pressure small angle neutron scattering and neutron-spin echo spectroscopy. As an important result it was found, that the stiffness of the membrane increases solely by an increase of the pressure.The waste of chemical solvents from chemical processing and related industries represent a huge environmental concern. During the last decades supercritical fluids have attracted much attention as potential replacements for these conventional organic solvents. Supercritical CO 2 (T c = 31.1 1C, p c = 72.8 bar) is seen as the most promising candidate because it is cheap, abundant, incombustible, non-toxic, bio-and foodcompatible. Unfortunately scCO 2 is generally a very poor solvent, in particular for polar and/or high molecular weight solutes. Thus, in applications where both polar and nonpolar components needed to be dissolved, emulsions and microemulsions were used to overcome this severe limitation. 1 Furthermore, scCO 2 microemulsions are also of great interest from a theoretical point of view because, contrary to classical ''state of the art'' microemulsions, the properties of scCO 2 microemulsions can be strongly influenced just by varying the pressure, i.e. the solvent properties of CO 2 . So far studies on these novel microemulsion systems concentrate on the phase behavior and the microstructure of CO 2 -rich microemulsions. 1-3Recently, we were able to formulate balanced supercritical CO 2 -microemulsions containing equal volumes of water and CO 2 using technical grade n-alkyl-polyglycolether-and perfluoroalkyl-polyglycolether-surfactants. 4,5 The phase behavior of such a microemulsion system H 2 O/NaCl-scCO 2 -Zonyl FSH/Zonyl FSN 100 is shown in Fig. 1 for pressures of p = 160 (top), 220 (middle) and 300 bar (bottom) as a function of the overall surfactant mass fraction g and the temperature T.5 Thereby the mass fraction a of CO 2 in the mixture of water and CO 2 was adjusted to a = 0.40 and the surfactant mixture consists of equal amounts of Zonyl FSH and Zonyl FSN 100 (d = 0.50). NaCl (1 wt% in the mixture of water and NaCl; e = 0.01) was added to screen possible electrostatic interactions induced by ionic impurities.As can be seen in Fig. 1 the phase behavior of this system resemble the phase behavior of well-known non-ionic microemulsions at ambient pressure.6 Thus, at low temperatures a CO 2 -in-water microemulsion coexists with a CO 2 -excess phase ( À 2), while at high temperatures a coexistence of a water-in-CO 2 microemulsion with a water-excess phase ( 2) is found. This phase inversion manifests itself in an extended three phase region which can be observed at intermediate temperatures and low surfactant weight fractions g. Increasing g the three phase region meets the one phase region at the so-called optimum point (g,T˜). It defines the minimum amount of surfactant needed to solubilize water and CO 2 at the phase inversion temp...

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