(162a) How Shear Impacts The Structure And Rheology Of Attractive Colloidal Systems

Colloidal suspensions with short-ranged attractions are known to exhibit nontrivial dynamic behavior [1]. For instance, such systems can display a diffusivity maximum at a constant colloid volume fraction when the attractive strength is varied. This behavior is indicative of the fact that these systems can form two glasses (a ?repulsive glass? and an ?attractive glass?) at the two extremes of interparticle attractive strength. The latter behavior has attracted significant attention and has been extensively studied using a variety of models and techniques. However, the manner in which such short-ranged attractions affect the rheological properties is still not well-understood and remains an open question. As should be expected, preliminary published experiments have indicated zero-shear viscosity goes through a minimum as a function of attractive strength [2]. The response of such systems under shear has, on the other hand, received little attention. We present comprehensive simulation results on the effects of attractive strength and shear-rate on the shear-viscosity and structural order of a model short-ranged attractive system. Specifically, we show that the shear-viscosity is strongly correlated to the underlying structural order. These results provide new insights into the connections between rheology and structure of this novel class of complex fluids.

[1] F Sciortino, Nature Materials, 1 (2002) 145. [2] V. Gopalakrishnan and C. F. Zukoski 48 (2004) 1321; L-N Krishnamurthy, NJ Wagner, J. Rheol., 49 (2005) 799