(151e) Effects of Concentration, Interaction and Shape Anisotropy On Dynamics of Colloidal Mixtures

Rules for equilibrium and non-equilibrium phase behavior of colloidal mixtures are not well understood. Theory and simulation have been used to predict phase diagrams and dynamics of colloidal mixtures formed by spherical particles with varied size ratios and interaction energies. Limited experimental work has been reported that can be used to compare with these theoretical and modelling predictions. In addition, neither theory nor experiment have  investigated the behavior of mixtures with shape anisotropy incorporated. Here a seeded emulsion polymerization method is used to produce large quantities of uniform particles with similar surface chemistry but varied shape and size. By coating the particles with a stabilizer, these particles experience weak attractions ionic strength ionic strength is increased. In our studies the mechanical properties of mixted dispersions are investigates for different number density ratios at increasing volume fraction for varied strengths of attraction and shape anisotropies. Our particular interest lies in characterizing these materials in the glassy and weak gel region. Mixtures are found to alter gel volume fractions and volume fraction dependencies of moduli, their frequency depends and yielding of glassy systems. This behavior will be discussed in terms of anisotropic interactions and changes of free volume in suspension introduced by mixing.