Rheological properties and structural correlations in particle-in-oil gels

摘要

Solid, hydrophobic matrices are used to increase the viscoelasticity of pharmaceutical products, cosmetics and foods. We have developed a method for transforming low viscosity oils into highly elastic solids. The solid is derived from an oil-in-water emulsion template where silanised fumed silica nanoparticles are attached to the droplet surfaces. Removing the water by freeze drying drives the template into a three dimensional network of particles in oil. The gels have oil contents as high as 98% due to the low concentration of particles required. We show that the gel elasticity is a power law function of the particle concentration, consistent with theoretical predictions. A key finding is that the gels can show strain thickening, an increase in elasticity under large applied strains. This is due to a sharp increase in the characteristic size of the gel microstructure above a critical particle concentration.