One-pot synthesis of sub-micron organosilicate particles for the formulation of Pickering emulsions

Abstract This work aims at describing the synthesis under mild conditions of amphiphilic aluminium/calcium organosilicate particles using a mixture of three organosilanes as starting material: tetraethoxysilane (TEOS), octyltriethoxysilane (OCTEO) and 3-[hydroxy(polyethyleneoxy)propyl]trimethoxysilane (4140). As opposed to the conventional synthesis, the method described here introduces a double functionalization of organosilicate particles with a tailored hydrophilic/hydrophobic ratio containing both aluminium and calcium within the inorganic layer. To investigate the influence of silane precursor ratio on the size of the particles and their ability to stabilize Pickering emulsions, we used a D-optimal mixture design methodology. The granulometric analysis revealed that the amount of OCTEO had a significant influence on obtaining visible particles, whereas successful syntheses presented a unimodal sub-micron mean distribution ranging from 650 nm to 3 μm. Elemental analysis, infrared spectroscopy (FT-IR), X-ray diffraction (XRD), transmission electron microscopy (TEM) and scanning electron microscopy (SEM) were used to more accurately characterize the organosilicates produced. Our results showed that a high concentration of hydrophobic silane led to particles that could stabilize concentrated water-in-silicone (W/Si) Pickering emulsions whereas more hydrophilic particles resulted in unstable silicone-in-water (Si/W) emulsions.