Dynamics of microemulsions adjacent to planar hydrophilic walls
H. Frielinghaus
1, F. Lipfert
2, M. Kerscher
2, O. Holderer
1, P. Busch
1, S. Mattauch
1, M. Monkenbusch
2, M. Belushkin
3, G. Gompper
3and D. Richter
1,21Jülich Centre for Neutron Science, Forschungszentrum Jülich GmbH, Lichtenbergstr. 1, 85747 Garching, Germany
2Institute for Complex Systems 1: Neutron Scattering, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany
3Institute for Complex Systems 2, and Institute for Advanced Simulations 2: Theory of Soft Matter and Biophysics, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany
E-Mail: h.frielinghaus@fz-juelich.de
Aqueous surfactant systems have manifold applications for the enhanced oil recovery. The micelle formation of the surfactant leads to high viscosities, which is desired for many reasons. The cracking fluid needs to deposit the hydrostatic energy in the sand stone close to the bore hole, and, thus, cracks are generated. The proppant consists of sand particles, which are left inside the cracks and keep the porosity high for better production rates after the application. The fluid itself forms a microemulsion when in contact with oil. The microemulsion possesses a low viscosity, which is favorable for the easy production.
The static structure of a bicontinuous microemulsion as a model complex fluid has been studied statically by GISANS and reflectometry experiments and in parallel by computer simulations [1]. A lamellar structure was induced by the planar wall. The high order decayed with growing distance from the wall and finally the bulk structure is bicontinuous. The decay of the lamellar order was realized by a growing number of perforations as observed by the simulations. The typical lengths of the decay and the onset of the perforations were compared between the different methods.
Dynamically, the grazing incidence method was transferred to neutron spin echo spectroscopy [2]. We found three times faster relaxations close to the wall in comparison to the bulk structure. The hydrodynamic waves are reflected by the wall, which explains the faster undulations of the surface near lamellae. Faster dynamics explain also a lower viscosity, which in this case is known as the lubrication effect. This effect would theoretically explain a slip length indicating a facilitated sliding off of the oriented lamellae. This in turn is highly interesting for flow fields of complex fluids in porous materials or for an initial state in the capture process of immune cells at vessel walls.
References
[1] M. Kerscher, P. Busch, S. Mattauch, H. Frielinghaus, D. Richter, M. Belushkin, G. Gompper, Phys. Rev. E 83, 030401 (2011)
[2] H. Frielinghaus, M. Kerscher, O. Holderer, M. Monkenbusch, D. Richter, Phys. Rev. E 85, 041408 (2012)
