Alkylcyanoacrylate nanocapsules prepared from mini-emulsions: a comparison with the conventional approach.

Polyalkylcyanoacrylate nanocapsules are being prepared using two different types of o/w-emulsions: a conventional emulsion generated by intensive stirring with a home-made device and a mini-emulsion produced by the action of ultrasonic dispersion, using the alkylcyanoacrylate monomer as a hydrophobic agent. The emulsions and the resulting nanocapsule dispersions are compared using various methods of physical characterization. The formation of solid capsules is indicated by solid state NMR spectra and atomic force microscopy. Differences between the results of both synthetic approaches are found in terms of particle size distribution, zeta potential and tendency towards particle agglomeration. Capsules prepared by ultrasound via the mini-emulsion pathway tend to be smaller and more monodisperse. Their zeta potential is negative with larger absolute values as compared to capsules obtained from conventional emulsions, leading to stronger repulsive interactions and a higher stability against capsule agglomeration.