Interaction Forces between Hydrophilic or Hydrophobized Silica Surfaces in Non-aqueous Media Studied by AFM

Abstract

We have measured the interaction forces between a pair of the hydrophilic or hydrophobized silica surfaces in the anhydrous non-aqueous medium of ethanol, toluene, or cyclohexane and in their moist media. In the case of toluene and cyclohexane, the strong adhesion forces were observed for a pair of the hydrophilic surfaces, whereas negligibly small adhesion forces were found for a pair of the surfaces hydrophobized by silane coupling agents with alkyl chains. The trace amount of water in these solvents enhanced the adhesion forces between the hydrophilic surfaces and between the surfaces hydrophobized by silane of short alkyl chain. The adhesion force between the surfaces hydrophobized by silane of long alkyl chains remained negligibly small even in the moist media. In the case of ethanol, no adhesion force was found between the hydrophilic silica surfaces, whereas the adhesion forces between the hydrophobized surfaces were relatively small.