Oil-in-water emulsions stabilized by Laponite particles modified with short-chain aliphatic amines

Liquid paraffin-in-water emulsions stabilized by Laponite RD clay particles modified with short-chain aliphatic amines (diethylamine, DEA or triethylamine, TEA) were prepared in the absence of electrolytes. The formation and stability of the emulsions were investigated by macroscopic and microscopic observations, contact angle, zeta potential and rheology measurements. The hydrophilic Laponite particles are rendered partially hydrophobic by the in situ surface modification with DEA and TEA. Contact angles, zeta potentials, and emulsion stability reach a plateau above a certain amine concentration, implying the full coverage of amine molecules on Laponite surface. At low clay concentration (0.5 wt%), stable emulsions can only be obtained when the clay–amine suspension is flocculated. And the attachment of the amine-modified particles on the droplet surface results in emulsion stabilization, which was observed by laser-induced fluorescent confocal micrographs. However, at high clay concentration (4.0 wt%), extremely stable emulsions form even the clay–amine suspension remains unflocculated. In this case, the emulsion stability can be attributed to the particle shell of the droplet, and more importantly, the gel structure of the suspension.