Inverse Pickering Emulsions with Droplet Sizes below
500 nm
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Abstract
Inverse Pickering emulsions with
droplet diameters between 180
and 450 nm, a narrow droplet size distribution, and an outstanding
stability were prepared using a miniemulsion technique. Commercially
available hydrophilic silica nanoparticles were used to stabilize
the emulsions. They were hydrophobized in situ by the adsorption of
various neutral polymeric surfactants. The influence of different
parameters, such as kind and amount of surfactant as hydrophobizing
agent, size and charge of the silica particles, and amount of water
in the dispersed phase, as well as the kind of osmotic agent (sodium
chloride and phosphate-buffered saline), on the emulsion characteristics
was investigated. The systems were characterized by dynamic light
scattering, transmission electron microscopy, cryo-scanning electron
microscopy (cryo-SEM), thermogravimetric analysis, and semiquantitative
attenuated total reflection infrared spectroscopy. Cryo-SEM shows
that some silica particles are obviously rendered hydrophilic and
form a three-dimensional network inside the droplets