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

Abstract

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 (${\mathrm{\ensuremath{\varphi}}}_{\mathrm{f}}$\ensuremath{\approx}0.50) we find the relative low-shear viscosity ${\mathrm{\ensuremath{\eta}}}_{\mathrm{r}}^{0}$ (low-shear viscosity normalized by the solvent viscosity) to be 53\ifmmode\pm\else\textpm\fi{}6, compared with results from previous studies that vary from \ensuremath{\approx}20 to 400.