(524e) Aggregation and Disintegration Model of Latex Colloids

Hydrodynamic interactions in colloidal dispersions have been analyzed by Stokesian dynamics (SD), the the lattice Boltzmann method (LBM), the finite element method (FEM), diffusion-limited aggregation, direct numerical simulations (DNS), stochastic rotational dynamics (SRD), fluid particle dynamics (FPD), dissipative particle dynamics (DPD) and fluid particle model (FPM). However, quantitatively reliable simulations have not yet been performed successfully for many-particle dispersions due to the complexity of the system. Recently, reliable and efficient numerical method, called the smoothed profile (SP) method to resolve the hydrodynamic interactions acting on solid particles immersed in Newtonian host fluids. In the SP method, the original sharp boundaries between colloids and host fluids are replaced with diffuse interfaces with finite thickness.

Dynamical processes occurring in the dispersion colloidal agglomerate in solvents are greatly influenced by coupling between the dispersed microstructures and the global flow. The average size of the agglomerated fragments depends on the shearing rate and the attractive forces between colloidal particles. The aggregation of colloidal particles is formed by the collisions between aggregates, which are influenced by the flow or by the cohesive forces for small dispersion energies.

If there are no significant steric or Coulombic interactions, the depth and range of the depletion interaction can be independently controllable. If Coulombic forces are present, adding salt can shrink the size of the Debye double layer, diminishing the repulsion until the colloids aggregate by van der Waals attraction. Sterically stabilized colloids can be cooled from high temperatures, causing the surface grafted polymer layers on the colloid to change conformation, again allowing the colloids to approach close enough to aggregate by the van der Waals attraction. Our colloids of latex went through aggregation and disintegration on shear deformation and were found to behave as elastic solids at low shear rates and require a finite stress to flow. The behavior of shear stresses is analyzed and modeled to dependent on zeta potential, shear rates and fractal floc size and compared with previous models.