Executive Summary
Controlling the elasticity of gelled systems has a large effect on their overall consistency and flow behavior . Previously, we demonstrated a general correlation between the rheology and structural rigidity of model colloidal gels in the nonlinear regime . This earlier work suggests that both central and tangential interactions (in the form of interparticle attraction and friction) play an important role in the flow properties of many colloidal and granular systems. Here, we adopt a two - pronged approach to exploring the effect of such interactions on the measured elasticity of gelled systems. In collaboration with Eric Furst and his group, we develop a model gel system that allows us to perform direct force measurements in parallel with bulk rheometry experiments. These interparticle interactions dictate the underlying gel microstructure and ultimately affect the overall elasticity. We also develop model PMMA colloids with controlled surface roughness to determine its effect on gel rheology. Our work suggests that roughness enhances the linear elasticity of gels, but the effect is significant only at high volume fractions.