Highly charged inorganic-organic colloidal core-shell particles.

Highly defined, hybrid inorganic-organic colloidal core-shell particles consisting of a silica core and a shell of fluorinated acrylate are prepared in a two-step route. The core-shell structure of the particles is investigated by means of small-angle X-ray scattering (SAXS). Because of highly acidic sulfonic acid surface groups resulting from the radical initiator sodium peroxodisulfate at the organic shell, long-range electrostatic interactions lead to the formation of liquidlike mesostructures. Increasing the effective interaction by reducing the next-neighbor distances induces a freezing of the liquidlike structures, i.e., a transition to crystalline and glassy structures. Because of the high electron density in the core and the fluorinated polymer shell, these particles are strong X-ray scatterers. In combination with the large number of effective charges and the outstanding monodispersity, these core-shell particles are a promising model system for the investigation of the glass transition by photon correlation spectroscopy employing coherent X-rays.