Evaluation of the Correlation between Surface Forces in Organic Solvents and Affinity of Solvent Molecules with Surfaces

Abstract

Various kinds of particle suspensions in organic solvents are used in a wide range of industries. Thus, characterizing interactive forces between solids in organic solvents is significant for handling such suspensions. However, while the DLVO theory well describes the interaction between surfaces in aqueous solution, the interactions between particles in non-aqueous solvents have been much less understood. In this study, we prepared silica surfaces modified with silane coupling reagents with various terminal groups and investigated the interactions between the modified particle and substrate in organic solvents by atomic force microscopy. We also conducted NMR relaxation measurements to evaluate the relationship between the interaction forces and surface-solvent molecule interactions. The repulsive forces acting over a few nanometers were measured between the surfaces when the particles disperse, whereas only van der Waals attraction was observed when the particles aggregate. This repulsive force was suggested to be the solvation force, arising from the steric hindrance of solvent molecules strongly attached to the surfaces, which was produced when the surface-solvent molecule interaction is strong. On the other hand, when van der Waals attraction dominated the interactions between the surfaces the surface-solvent molecule interaction was found out to be weak.

Graphical Abstract