Polymer-coated cationic silica nanoparticles for slow-release Pickering emulsions


Silica nanoparticles were functionalized with amine and quaternary ammonium groups using a two-step chemical surface modification, to allow coating with anionic polymers for emulsion stabilization. This strategy proved to render high colloidal stability in aqueous dispersions and strong electrostatic interactions with polyacrylic acid and poly(sodium 4-styrene sulfonate), over a wide pH range. These hybrid nanoparticles stabilized Pickering emulsions at very low concentrations (0.01 wt%), without added surfactants. Most stable emulsions were obtained with nanoparticles coated with polyacrylic acid, due to synergy of strong interfacial adsorption of nanoparticles enhanced by the long polymeric chains and the weak polyelectrolyte character of the polymer. These nanoparticles were able to prevent diffusion of N,N′-diethyl-m-toluamide (DEET), a common insect repellent, from oil-in-water emulsions into a model media. The release profile followed typical zero-order kinetics, demonstrating the potential of using the polymer-coated nanoparticles developed in this work in DEET formulations to achieve extended repellent action.

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The authors would like to thank Tiago Venâncio (UFSC) and Naira Ruiz (PUC-Rio) for solid NMR measurements. L.D.B. thanks the Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq, Brazil) for the scholarship.


This study was financed, in part, by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES, Brazil)—Finance Code 001 and the Royal Society (Royal Society-Newton Mobility Grant—160062).

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Daza, L.M., Percebom, A.M. & Pérez-Gramatges, A. Polymer-coated cationic silica nanoparticles for slow-release Pickering emulsions. Colloid Polym Sci 298, 559–568 (2020). https://doi.org/10.1007/s00396-020-04639-y

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  • Silica
  • Particles
  • Quaternization
  • Polyelectrolytes
  • Emulsion
  • Controlled release
  • Insect repellent