(532g) Rheology of Particle Suspensions in Viscoelastic Fluids

The extensional rheology response of suspensions in viscoelastic fluids and the influence of matrix viscoelasticity on suspended particle dynamics remain less well-understood. Many formulations, including paints, coatings, cosmetics, foodstuff, and biological fluids, form examples of suspensions in viscoelastic fluid. This contribution contrasts the response of particle-laden solutions prepared with colloidal silica particles in two viscoelastic fluid systems based on polyethylene oxide and 2-hydroxyethyl cellulose. A strikingly distinct response was found in both shear and extensional flows characterized using torsional rheometry and capillarity-driven extensional flows using DoS rheometry, respectively. We present the visualization and analysis of pinching dynamics and rheology of particle suspensions, systematically comparing the dilute solution response to existing theoretical models. We elucidate the influence of polymer-particle interactions and macromolecular properties of the suspending fluid on the rheology and pinching dynamics and discuss the implications for dispensing macromolecular complex fluids.