The role of surfactant in controlling particle size and stability in the miniemulsion polymerization of polymeric nanocapsules

The influence of surfactant concn. on particle size and stability of nanocapsules with liq. cores, synthesized by an in situ miniemulsion polymn. process, was investigated. Although the role of surfactant in the synthesis of particles in the nanometer range has frequently been documented, the transition to structured particles, which almost consist of a 1:1 wt. ratio of encapsulated liq. hydrophobe to polymeric shell, has not received much attention. Capillary hydrodynamic fractionation (CHDF) analyses were used to evaluate particle size. Results were subsequently used to stoichiometrically calc. the area which is occupied per surfactant mol. on the particle surface. These results were compared with \"classical\" miniemulsion data, i.e., data generated from the synthesis of polymeric latexes in the presence of a hydrophobe, but at a much lower hydrophobe:monomer ratio as was used here. The surface coverage per surfactant mol. could be related to the surface tension of the latex, thus providing a relationship between particle size and stability. CHDF was furthermore used to investigate particle size after grafting of a secondary PMMA shell. Data obtained from CHDF expts. were in all cases confirmed by TEM anal. of the synthesized particles. To conclude, the synthesis of nanocapsules with liq. cores could be successfully scaled-up, with retention of all the characteristics of the final latex