NEW SURFACES AND TECHNIQUES FOR STUDIES OF INTERPARTICLE FORCES

Several methods of preparing surfaces suitable for interparticle surface forces measurements are presented. Treatment of muscovite mica surfaces with a water vapour plasma introduces surface hydroxyl groups. These groups can react with chlorosilanes to form organo functionalized surfaces. The forces between water vapour plasma treated mica surfaces in aqueous solutions are well described by DLVO theory except for the presence of a short-range (D < 10 angstrom) additional repulsion. After reaction with a fluorocarbon containing silane the surfaces become hydrophobic and a long-range attraction acts between the surfaces in water. Smooth glass spheres can be obtained by melting a glass rod in a gas burner. These surfaces are ideal substrates for a new type of surface force apparatus that uses a bimorph force sensor for measuring surface forces. The chemistry of the glass surfaces is readily modified by reactions with chlorosilanes. The similarities and the differences between the forces acting between glass and water vapour plasma treated mica surfaces before and after silanation are discussed. We also report on the use of a cold plasma process to produce thin, smooth organic films that can be investigated with the surface force technique.