Quantification of the structure of colloidal shared-solvent fluid–fluid interfaces
We have quantified experimentally the width and structure of the colloidal gas–liquid interface. Our model system comprises spherical colloids that are sterically stabilized in an apolar solvent. Colloidal gas–liquid phase-separation is induced through the depletion interaction, i.e., by addition of nonadsorbing polymer. The broadness of the resulting colloidal gas–liquid interface was probed using synchrotron X-ray reflectivity measurements at various points in the phase diagram. We find that the interfacial width is comparable to the size of the colloidal particles and that it scales in a meanfield fashion with the density difference. Our results further suggest that the density profiles are monotonic. The experimental results show excellent agreement with theoretical predictions based on free-volume theory and highlight that X-ray reflectivity experiments can be used to shed light on the intricate structure of these colloidal interfaces.
M. Vis1,2,3, J.H. Brouwer1,2,4, A. González García4,1,2, A.V. Petukhov4,1, O. Konovalov5, R. Tuinier1,2,4
1 Laboratory of Physical Chemistry, Eindhoven University of Technology, The Netherlands 2 Institute for Complex Molecular Systems, Eindhoven University of Technology, The Netherlands 3 Laboratoire de Chimie, ENS de Lyon, France 4 Van ’t Hoff laboratory for Physical and Colloid Chemistry, Debye Institute for Nanomaterials Science, Utrecht University, The Netherlands 5 European Synchrotron Radiation Facility, Grenoble, France
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