Steric Stabilization of Pickering Emulsions for the Efficient Synthesis of Polymeric Microcapsules

It is commonly known that Picketing emulsions ale extremely stable against coalescence and are, therefore, potentially interesting for the synthesis of new materials, such as colloidosomes, microcapsules, composite pal tides, foams, and so on However, for the efficient synthesis of such materials, one also has to consider the colloidal stability against aggregation, which is often neglected In this study, it is demonstrated that steric stabilization is provided to Pickering emulsion droplets by the adsorption of poly(styrene-block-ethylene-co-propylene) (pS-b-EP) and that it is a requirement for the efficient synthesis of polymeric microcapsules Monodisperse polystyrene particles of 648 nm are synthesized by soap-free emulsion polymerization A model Pickering emulsion is then formed by the addition of sodium chloride at a critical concentration of 325 mM and mixing it with either heptane or decane Subsequently, pS-b-EP is added to the Pickering emulsion to pi vide stem: stabilization Size exclusion chromatography is used to prove and quantify the adsorption of pS-b-EP onto the Pickering emulsion droplets. A maximum surface coverage of 13 mg/m(2) is obtained after 2 h, which is approximately one-third of the adsorption on a pure pS surface We believe that the presence of polar sulfate groups on the particle, which in stabilized the particle in water, reduces the adsorption of pS-b-EP Microcapsules are formed by heating the Pickering emulsion above the glass-transition temperature of the pal tidies Significant aggregation is observed, if no pS-b-EP is used The adsorption of pS-b-EP provides steric stabilization to the Pickering emulsion droplets, reduces aggregation significantly, and ultimately leads to the successful and efficient synthesis of pS microcapsules.