Solvation Forces and Rigidity in Dense Suspension Flows

Suspensions are mixtures of solid particles in a liquid medium. As the volume fraction of the suspending particles approaches the maximal jamming packing fraction, $\phi_J$, the material properties of these seemingly simple systems can exhibit discontinuous shear thickening (DST) where the viscosity increases discontinuously with shear rate, and even transition to a solid in a process known as shear jamming (SJ). Despite being simple and ubiquitous systems, many open questions in suspension science remain. Among them are the following questions: how do nanoscale and chemical features of the suspended particles and suspending media impact the bulk flow and solidification behavior, how do rigid frictional force networks inside suspension flow impact dissipation, and how do suspended particles with similar chemical characteristic but different morphological characteristics differ in their non-Newtonian flow behavior. This work touches on all three of those questions and finds new solvent chemical knobs to tune shear thickening and shear jamming, new phases of suspension flow where solid structures are embedded in flowing systems, and similarities and differences between different starch suspensions. This dissertation provides fundamental insights into how to control dense suspension systems using the chemistry of the suspending solvent, understand new dissipation mechanisms beyond interparticle forces, and insights into how different starch systems can show dramatically different rheological responses.