Concentration dependence of the low-shear viscosity of suspensions of hard-sphere colloids

Experimental measurements are presented of the concentration dependence of the low-shear limit viscosity of nearly monodisperse polymethylmethacrylate spheres dispersed in cis-decalin, a system that models a suspension of hard spheres. The suspension volume fractions are calibrated with reference to the volume fraction at which the particles undergo the thermodynamic freezing transition to a colloidal crystal, providing accurate estimates of the volume fractions of concentrated suspensions. At the freezing volume fraction (${\mathrm{\phi }}_{\mathrm{f}}$≈0.50) we find the relative low-shear viscosity ${\mathrm{\eta }}_{\mathrm{r}}^0$ (low-shear viscosity normalized by the solvent viscosity) to be 53±6, compared with results from previous studies that vary from ≈20 to 400.