Emulsification of particle loaded droplets with regard to miniemulsion polymerization

Composite nanostructured particles can be produced by polymerization of particle-loaded miniemulsion droplets. Breaking-up particle-loaded droplets is a challenge, because an increased viscosity and abrasiveness of the droplets has to be handled. Additionally, agglomerates in the droplets hinder their deformation and break-up and lead to large, non-spherical droplets. In this article, we show that high pressure homogenization is a promising process. If agglomerates are eliminated, droplets with encapsulated inorganic nanoparticles can be broken up to small sizes (here, droplets with 50 wt.% silica nanoparticles to sizes below 300 nm). Abrasion on the high pressure pump and the disruption unit can be avoided using a high pressure post feeding valve. In miniemulsion polymerization the surfactant concentration has to be adjusted to avoid secondary nucleation, which would result in the formation of unfilled plain polymeric particles. The required surfactant concentration is influenced by the particle load, in particular by particle surface-functionalizing molecules. To eliminate this, the surface modification of the nanoparticles was adjusted. Thus, homogeneous hybrid particles could be prepared. (C) 2013 Elsevier B.V. All rights reserved.