Preparation and properties of optically transparent aqueous dispersions of monodisperse fluorinated colloids

We report the emulsion polymerization and seeded growth of negatively charged, monodisperse fluorinated latex spheres in water with radii in the range 50-700 run. Due to their low refractive index (n(p) = 1.3660), the spheres can be index matched in aqueous media, without any complications due to (optical) polydispersity or specific solvent adsorption. Such index-matched dispersions of fluorinated latex allow study of the structure and dynamics of strongly interacting charged colloids in water, using light scattering or microscopy. Moreover, we prepared core-shell particles with fluorinated latex shells and optically anisotropic PFA (tetrafluoroethylene copolymerized with perfluoroalkylvinyl ether) cores. We demonstrate with depolarized light scattering that these cores allow for measurement of rotational self-diffusion. The fluorinated latex dispersions are characterized extensively using light scattering, electron microscopy, atomic force microscopy, and electrophoresis. Optical contrast variation is used to determine the particle refractive index and to demonstrate that the particles are optically homogeneous.