Ostwald ripening of nanoemulsions stopped by combined interfacial adsorptions of molecular and macromolecular nonionic stabilizers

Aliphatic hydrocarbon oil-in-water nanoemulsions were prepared using mixtures of an amphiphilic nonionic polysaccharide (dextran modified by covalent attachment of hydrocarbon tails) and tetraethylene glycol dodecylether as stabilizers. Nanoemulsions stabilized by amphiphilic polysaccharide alone underwent Ostwald ripening. On the contrary, nanoemulsions prepared with certain mixtures of hydrophobically modified dextran and tetraethylene glycol dodecylether exhibited no significant variation of their average droplet diameter over a period of time that depended strongly on the nature of the dispersed oil. When changing from n-hexane to n-octane and n-dodecane, the period of complete inhibition of Ostwald ripening varied from 3 h to several months. Polymer–surfactant interactions and co-adsorption at oil/water interface were demonstrated by dynamic interfacial tension measurements and dilational surface rheology.