Internally Self-Assembled Submicrometer Emulsions Stabilized by Spherical Nanocolloids: Finding the Free Nanoparticles in the Aqueous Continuous Phase

This article reports on the behavior of colloids during the stabilization of internally liquid-crystalline droplets. The ability and limitations of spherical silica colloids to act as stabilizers of liquid-crystalline bulk phases have been demonstrated for monoglyceride/tetradecane/water and phytantriol/tetradecane/water systems using small-angle X-ray scattering and dynamic light scattering as probes. It has been demonstrated that these nanoparticles are very good stabilizers of phytantriol-based phases. In particular, these data showed that they are nondisruptive stabilizers for these bulk phases at ambient temperature. Interestingly, it was shown that the spherical nanoparticles were not able to stabilize the monoglyceride-based bicontinuous cubic phase (Pn3m symmetry group), in contrast with their phytantriol-based counterparts. They were, however, good stabilizers of the monoglyceride-based emulsified microemulsions and inverse micellar cubic phases (Fd3m symmetry group). We then further examined the influence of the concentration cif stabilizer on the phytantriol-based dispersed particles. We showed that the scattering signals of the liquid crystal and the nanoparticles are uncorrelated, whatever the identity of the liquid-crystalline phase. A careful analysis method coupled with dynamic light scattering measurements allowed us to determine and discriminate qualitatively the cases with or without five nanoparticles in the continuous phase. The results indicate for the first time fundamental differences in the stabilization by solidlike nanoparticles of emulsified microemulsions and of bicontinuous cubic phases.