Influence of the electrostatic interactions in a Pickering emulsion polymerization for the synthesis of silica-polystyrene hybrid nanoparticles.
OBJECTIVE
Silica-polystyrene hybrid nanoparticles were synthesized by Pickering emulsion polymerization. The coupling effect of initiator type and silica surface charge was studied to exhibit the predominant role of electrostatic interactions in the synthesis mechanisms.


METHODS
Non-ionic hydrophobic initiator (2,2'-azobis(2-methylpropionitrile), AIBN) or anionic hydrophilic initiator (sodium persulfate, NaPS), and positively or negatively charged silica were used as reactants with styrene for Pickering emulsion polymerization. Their interactions were evaluated by Zeta potential measurements. The droplet size and the stability of the Pickering emulsions, and the hybrid particle morphology, surface coverage, size and agglomeration were evaluated by laser granulometry and microscopy.


RESULTS
Similar surface charge between negatively charged silica particles and an anionic initiator led to strong repulsions and thus to non-covered polystyrene nanoparticles. With positively charged silica, a high decoration was obtained due to attractive interactions between the inorganic and the organic phases, but a strong agglomeration was also observed. The use of a non-ionic initiator led to a homogeneous coverage with negatively charged silica. With positively charged silica micronic sizes were formed by following two different mechanisms. These data, by enriching the existing literature, led to a more complete and robust description of the emulsion polymerization synthesis for hybrid nanostructures.
Laboratoire Science des Procédés Céramiques et de Traitements de Surface (SPCTS), UMR CNRS 7315, ENSCI, Centre Européen de la Céramique, 12 rue Atlantis, 87068 Limoges Cedex, France.
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Monégier du Sorbier
Laboratoire Science des Procédés Céramiques et de Traitements de Surface (SPCTS), UMR CNRS 7315, ENSCI, Centre Européen de la Céramique, 12 rue Atlantis, 87068 Limoges Cedex, France. Electronic address: anne.aimable@unilim.fr.
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Aimable
Laboratoire Science des Procédés Céramiques et de Traitements de Surface (SPCTS), UMR CNRS 7315, ENSCI, Centre Européen de la Céramique, 12 rue Atlantis, 87068 Limoges Cedex, France.
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Pagnoux
Hybrid nanoparticles; Pickering emulsion polymerization; Polystyrene; Silica; Surface charge