Hydrophobized Colloidal Silica: Effect of Functional Group and Surface Coverage on Particle Wettability and Pickering Emulsion Stabilization

ABSTRACT

     The surface of colloidal silica nanoparticles is populated with hydroxyl groups that provide excellent anchoring sites for chemically-bonded surface modifiers. In particular, alkyl chlorosilanes can be used to hydrophobically modify silica surfaces, altering their wettability and increasing their ability to stabilize Pickering emulsions. This study seeks to investigate how particle wettability changes as a function of both fractional surface coverage and type of alkyl group. Fractional surface coverage was quantified using H NMR and particle wettability was quantified using three different methods: drop-shape analysis, the Washburn method for measuring powder wettability, and a calorimetric method using heat of immersion. The ability of these particles to stabilize Pickering emulsions and their location at the oil-water interface has also been probed using electron and light microscopy.