The role of functional monomers on producing nanostructured lattices obtained by surfactant-free emulsion polymerization – A novel approach

Nanostructured lattices were prepared in a single step emulsion polymerization reaction in the absence of surfactants by exploring the so called “pickering” stabilization mechanism. The synthesis protocol and the properties of the obtained particles were evaluated and discussed simultaneously considering processing and formulation aspects with special emphasis to the chemical properties of the functional monomers selected on the present study. Colloidal silica was used to ensure the physical stability required to produce nanoparticles as a result of the emulsion polymerization route. Three different monomers including methyl metacrylate (MMA), styrene (Sty) and vinyl acetate (VAC) were used to structure the particles of interest. Four different functional polymers including acrylic acid (AA), styrene sulfonate (StySO3), hydroxyethyl methacrylate (HEMA) and dymethylamino ethyl methacrylate (DMAEMA) were evaluated.The obtained lattices were comparatively characterized regarding to surface tension, particle size distribution, morphological aspects, viscosity, zeta potential and colloidal stability.The one-step pickering emulsion polymerization proved to be an effective approach to prepare lattices of industrial interest without the use of surfactants. The obtained particles presented average mean diameters ranging from 155 to 345 nm with relatively low polydispersity indices (0.39–2.02). The most promising behavior was experimentally verified once selecting the styrene sulfonate (StySO3) as the functional monomer. The hydroxyethyl methacrylate (HEMA) also proved to be an interesting alternative although its limitation related to high surface tension applications. The high resolution images registered with the HRSEM-FEG technique explicit morphological aspects that effectively contribute to elucidate the “pickering” stabilization mechanism and the resultant core–shell structure derived thereof.

Schematic illustration of synthesis and SEM characterization of lattices produced by surfactant-free emulsion polymerization.Figure optionsDownload as PowerPoint slide