SKM 2021 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 6: Poster Session II

CPP 6.2: Poster

Tuesday, September 28, 2021, 17:30–19:30, P

Direct Measurement of the Forces Acting Between Colloidal Silica Particles — •Thomas Tilger, Michael Ludwig, and Regine von Klitzing — Department of Physics, Technische Universität Darmstadt, Darmstadt, 64289, Germany

Natural colloidal dispersions have accompanied mankind in the form of blood or milk ever since. Besides this, artificial systems have gained a significant importance for our daily life during the last decades. From the production of many cosmetics or the water purification and sewage water treatment to the medical field, colloidal systems are widely used nowadays.

For all these applications, it is of special interest to gain an understanding of which interparticle forces govern the stability of colloidal dispersions and how this stability can be tailored. In electrolyte solutions, the classical DLVO theory describes these interactions as a superposition of van der Waals and electrostatic double layer forces. Complex fluids such as micellar dispersions show additional oscillatory contributions caused by a structuring of the micelles.

For a detailed examination of these two regimes, we directly measure the forces between two colloidal silica particles in aqueous solutions by the colloidal probe AFM (atomic force microscopy) technique. Varying the concentration of sodium chloride solutions allows us to compare the transition from the double layer to the van der Waals dominated regime with the predictions of the DLVO theory. Similar measurements for the anionic surfactant sodium dodecyl sulfate (SDS) reveal a structuring of the SDS micelles under confinement.