Attractive glass formation in aqueous mixtures of colloidal gibbsite platelets and silica spheres

We present an experimental study on the attractive glass formation in mixtures of colloidal gibbsite platelets and silica spheres. The platelets are 233 nm in diameter, and the diameter ratio between the platelets and the spheres is 13.8. The glass formation is induced by the short-ranged depletion attraction caused by the spheres. At sufficiently high sphere concentrations the depletion attraction is strong enough that the mixtures do not form the equilibrium liquid-crystalline phases, but the glass formation occurs instead. Using microradian X-ray diffraction measurements we provide detailed information about the structure of the arrested glass state. In mixtures with weaker depletion it consists of liquidcrystalline pockets embedded in the less ordered glassy surrounding. With a stronger attraction in the system the size of these domains decreases, until the structure of the attractive glass becomes completely disordered and isotropic.