Dense suspensions and mixtures of particles of various shapes and tunable interactions find diverse applications in materials science and engineering. We have developed microscopic statistical mechanical theories for the intermittent activated and coupled translational-rotational dynamics of uniaxial colloids as a function of aspect ratio, strength of attractions, and degree of chemical heterogeneity (Janus colloids) under both quiescent and strongly deformed conditions. Criteria for the emergence of nonequilibrium gels, attractive glasses, repulsive glasses and plastic glasses, and their elastic properties and stress-driven yielding behavior, have been studied. Predictions for how repulsive force caging, physical bond formation and shape anisotropy lead to new types of nonequilibrium phase diagrams, two-step relaxation associated with translation-rotation decoupling, and unusual double yielding will be described. The evolution of the shear modulus in different regions of the nonequilibrium phase diagram has also been determined. Quantitative comparisons of the theoretical results with experiments will be presented. Most recently, the theory has been extended to dense mixtures of spheres and rods where the connectivity percolation threshold and statistical microstructure can be widely tuned. These systems are of interest in diverse contexts that range from functional inks for direct write printing applications to various biophysical contexts. New dynamical complexity emerges that is triggered by packing asymmetry, including the formation of rod gel networks where the spheres can be either co-localized or fluid depending on interactions, rod aspect ratio and mixture composition.

Activated dynamics, kinetic arrest, elasticity, and yielding in dense colloidal suspensions

246th National Meeting (2013)

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