Titanium dioxide-polymer core-shell particles dispersions as electronic inks for electrophoretic displays
Résumé
The preparation of inorganic-organic core-shell particles is presented. These particles, composed of a titanium dioxide core and a polymer shell, are prepared via precipitation polymerization and inverse microsuspension polymerization. The electrical and optical properties of dispersions of these particles in a paraffin oil are measured in view of the formulation of electronic inks for electrophoretic displays. Encapsulation of TiO2 by precipitation polymerization is improved by pretreating the pigments with 3-(trimethoxysilyl)propyl methacrylate, making it possible to prepare particles with a TiO2-to-polymer ratio varying over a wide range. This ratio has a considerable influence on the optical properties of the dispersion but also on the interactions between pigments and electrodes. The polymer shell can then be further functionalized by introducing acidic groups at the particle's surface. Encapsulation of the TiO2 can also be achieved by inverse microsuspension polymerization of poly(sodium acrylate), allowing the introduction of the acidic groups in one step only. Finally, dispersions of TiO2-polymer particles in black dyed paraffin oil have successfully been applied in an A4-sized segmented electrophoretic display panel.