Synthesis of sterically stabilized perfluorinated aqueous latices

We report on two novel and improved reaction strategies for the synthesis of a recently introduced new colloidal model system [M. Wiemann, R. Schneider, E. Bartsch, Z. Phys. Chem. 226 (2012) 761] composed of cores of the highly fluorinated polymer poly(1H,1H-heptafluorobutyl methacrylate) (PFBMA) and sterically stabilized in water by a poly(ethyleneglycol) (PEG) coating. PFBMA was chosen as its low refractive index allows to prepare highly concentrated dispersions isorefractive in aqueous medium which makes such systems amenable to light scattering studies. In the first approach we use standard emulsion polymerization for synthesis of a PFBMA seed dispersion. The seed particles are then functionalized in a seeded growth polymerization with a thin shell composed of the bromine carrying monomer 2-(2-bromoisobutyryloxy) ethyl methacrylate (BIEM) co-polymerized with FBMA. BIEM is an initiator for atom transfer radical polymerization (ATRP) which is used in the final step to graft the particle surfaces with PEG using the macromonomer poly(ethyleneglycol) methacrylate (PEGMA, DP = 23). In the second approach we combine seed preparation and functionalization into one step with a semi-batch emulsion polymerization, generating a core–shell particle with PFBMA as core and a P(BIEM-co-FBMA) shell, again followed by ATRP to graft PEG onto the particles. Both strategies provide nearly monodisperse particles which are sterically stabilized in water as demonstrated by dynamic light scattering experiments in combination with colloidal stability tests and H- 1 NMR characterization. The merits and disadvantages of these new synthesis strategies for the preparation of model colloids are critically compared.