Rheology of polyampholyte (gelatin)-stabilized colloidal dispersions: The tertiary electroviscous effect

The shear rheology of gelatin-stabilized acrylic and polystyrene latices is investigated as a function of particle concentration, electrolyte concentr ation, and pH. Independent measurements of the adsorbed polyampholyte amoun t and layer structure are used to predict the rheology within the context o f hard-sphere mappings. Dynamic light-scattering measurements of the hydrod ynamic particle diameter of gelatin-coated colloids yield the best predicti ons of the zero-shear viscosity and can qualitatively predict the observed tertiary electroviscous effect. Comparisons between dispersions demonstrate the effect of hydrophobic anchoring of the adsorbed gelatin on dispersion rheology. (C) 2001 The Society of Rheology.