Rheology of Jammed Silicone Microgels

Colloidal and granular-scale hydrogel particles have been widely used to study jammed and glassy matter in systems with soft inter-particle potentials. Aqueous microgels are most commonly used for these investigations and a diversity of chemical formulations have been developed for controlling inter-particle interactions, microgel size, and particle stiffness. However, there are numerous industrial applications of non-aqueous microgels, creating the need for the fundamental understanding of the rheology of jammed non-aqueous microgels. In this presentation, we will describe our investigations of polydimethylsiloxane (PDMS) microgels. We synthesize PDMS microgels using several different silicone formulations and swell them to a jammed state in silicone oil. The size and the shape of the microgels are varied during synthesis and the resulting effect on the rheological properties of the microgels are studied. By independently varying microgel composition and solvent viscosity, we can independently tune the yield stress and flow characteristics of this jammed system.