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Force measurements between Teflon AF and colloidal silica particles in electrolyte solutions
Authors:Astrid Drechsler  Nicole Petong  Junfeng Zhang  Daniel Y Kwok  Karina Grundke  
Institution:

aInstitute of Polymer Research Dresden e.V., Hohe Strasse 6, 01069 Dresden, Germany

bNanoscale Technology and Engineering Laboratory, Department of Mechanical Engineering, University of Alberta, Edmonton, Alberta, Canada T6G 2G8

Abstract:The interaction force between a very hydrophobic polymer surface and colloidal silica particles with a roughness of 10–15 nm has been measured in aqueous solutions of KOH and KCl using an atomic force microscope. The interaction can be described according to the DLVO theory by an electrical double-layer force that is repulsive at long distances and attractive at short distances and an attractive van der Waals force. The electrical double-layer potentials are compared to the zeta potentials of Teflon AF and the silica spheres. The roughness of the silica particles leads to an underestimation of the short-range attraction and the surface potential. Both KCl and KOH solutions affect the potential of the interacting surfaces. OH? ions that adsorb preferentially to the Teflon AF surface create higher potentials than Cl? ions. Range and strength of the attractive interaction are not affected by KCl solutions but reduced by addition of KOH. This can be explained by decreasing potential differences between the silica sphere and Teflon AF with increasing KOH concentration. In addition, the preferential adsorption of OH? ions may lead to a reduction of the van der Waals interaction. The presence of nanobubbles, too, might play a role.
Keywords:Surface forces  DLVO theory  Teflon AF  Silica  Atomic force microscopy
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