Preparation and properties of dispersions of colloidal boehmite rods

Abstract

Dispersions of colloidal boehmite (y-AlOOH) rods (of controllable length) are prepared from alkoxide precursors. A polyisobutene grafting procedure leads to sterically stabilized dispersions. In the organophilic system (L ~ 200 nm ± 50%; D ~ 10 nm ± 25%) an isotropic-nematic phase separation is observed for boehmite volume fractions between 3.8% and 14.6%. The effect of polydispersity on the phase diagram is well predicted qualitatively by Onsager's theory extended to bidisperse mixtures.