Viscosities of colloidal spheres, i.e., colloidal silica (diameter 8 and 45 nm) and monodisperse polystyrene latices (diameter 85 to 780 nm), are measured indeionized(lsquo;lsquo;salthyphen;freersquo;rsquo;) suspensions and in the presence of a small amount of NaCl. The reduced viscosities (specific viscosity divided by concentration) of deionized silica (diameter 8 nm) are much higher than would be expected by Einsteinrsquo;s prediction anddecreasesharply with increasing concentration. A sharp peak is observed in the reduced viscosity vs concentration curves of deionized colloidal silica of 45 nm diameter and the deionized latex spheres. The peak corresponds to the transition between lsquo;lsquo;liquidhyphen;likersquo;rsquo; and lsquo;lsquo;crystalhyphen;likersquo;rsquo; structures. These results show that electrostatic intersphere repulsion and the elongated Debyehyphen;screening length around the colloidal spheres are essential to explain the extraordinary properties.
展开▼
