Shear Rate Dependent Structure of Polymer Stabilized TiO$_{2 }$ Dispersions - 1. TiO$_{2}$ Structure

We measured the shear rate dependent structure of TiO$_{2}$ dispersions (37{\%} volume fraction) stabilized with commercial polymer dispersants in water. The TiO$_{2}$ is a commercial grade TiO$_{2}$ with a particle diameter of approximately 400 nm (when the dispersions were diluted and measured by Nanotrac 150). The solvent compositions were adjusted to the contrast match point of each dispersant to isolate the behavior of the TiO$_{2}$. Two different molecular weight poly acid dispersants (Referred to as ``low MW acrylate polymer salt'' and ``high MW acrylate polymer salt'') and two different molecular weight alkali soluble acrylate copolymers (Referred to as ``low MW hydrophobic acrylate copolymer salt'' and ``high MW hydrophobic acrylate copolymer salt'') were used in this study. The experiments were conducted at the NIST Center for Neutron Research (NCNR) on the perfect crystal diffractometer (PCD) for ultra-high resolution small-angle neutron scattering (USANS) measurements. The results for the TiO$_{2}$ scattering show that shear induced agglomeration occurs for certain dispersants and shear induced breakup of TiO$_{2}$ aggregates is observed for other dispersants. The results suggest new ways to consider dispersion of particles.