Styrene-in-Water Emulsions Stabilized Solely by SiO2 Nanoparticles with Tunable Wettablity

Abstract

Hydrophilic SiO₂ nanoparticles were modified by ethacryloxypropyltrimethoxysilane (MPTMS). The surface wettablity was tuned by controlling the grafting extent of MPTMS and the surface element content was confirmed by XPS. Through measuring the contact angle, the surface wettablity was investigated. The results showed that when the mass ratio of MPTMS to SiO₂ was 5 %, the contact angle was about 85º and the SiO₂ nanoparticles could be partly wetted by both phases. The modified SiO₂ nanoparticles were applied to stabilize styrene-in-water Pickering emulsion. The effect of surface wettability, particles concentrations on the stability and morphology of the Pickering emulsions was systematically studied. It was found that only SiO₂ nanoparticles partly wetted by both phases were suitable to form Pickering emulsion and stable emulsion could not be obtained until the SiO₂ nanoparticles concentrations were above 2 %.