PREPARATION OF A NONAQUEOUS DISPERSION OF STERICALLY STABILIZED BOEHMITE RODS

A poly(isobutene) grafting procedure is described which leads to sterically stabilized dispersions of (fairly monodisperse) boehmite needles in toluene and cyclohexane. The procedure employs a gradual change in solvent composition, transferring the boehmite from water to the organic solvent without loss of colloidal stability. The presence of firmly attached (modified) poly(isobutene) on the boehmite needles is clearly established with various techniques, such as infra-red spectroscopy and elemental analysis, as well as flocculation tests. The change from electrostatically stabilized needles in water to grafted needles in cyclohexane is manifested by a marked reduction in viscosity, and a decrease in the relaxation time of streaming birefringence.