(686a) Exploring and Manipulating Dense Packing Properties of Particles in Different Continuous Phase

When introducing size polydispersity or concentrating colloid dispersion quickly, dynamic arrested state has been entered with particles packing randomly without formation of long range order to create crystal phase. In this region, the long range diffusivity of the particles is greatly hindered by cooperative motions. Developed knowledge in this dense packing state is important for practical application considering the potential in designing materials with novel optical and mechanical properties. Efforts have been made in the past to understand the relaxation behavior of colloidal dispersions in this dynamic arrested state both theoretically and experimentally. However, no conclusion has been drawn to explain the dynamics of colloids when approaching the condition where the dispersion cannot be processed. Here we use rheology study to explore the dynamics of colloid in different continuous phases when approaching the maximum processable volume fraction. Results of linear elasticity, yielding stress and nonlinear rheology are compared to understand the short-range diffusion and long-range relaxation to ultimately explain the macroscopic change tendency near the volume fraction where dispersions cannot flow. Different continuous phases are applied to control the particle interaction which is deformed when bringing particles into close proximity. Of particular interest is our ability to alter the particle maximum dense packing volume fraction by working with a binary mixture of particles where we vary the fraction of the total volume fraction occupied by a certain species, and different behavior of this binary mixture is also observed in flow properties compared to homogeneous colloidal dispersions.