Tuning Solvent Chemistry to Suppress Shear-Jamming in Dense Suspensions

Mechanical stress can transform a free flowing suspension of solid particles in a Newtonian liquid into a shear jammed, solid-like state. While recent work highlighted how particle surface chemistry contributes to the shear jamming transition,[1] much less is known about the suspending liquid. We here report both steady state rheology and the transient impact response tracked by high-speed ultrasound imaging [2] for silica nanoparticles dispersed in polyethylene glycols (PEGs) of varied chain lengths. For suspensions with identical silica volume fractions and impact conditions, decreasing the solvent molecular weight (MW) suppresses shear jamming. We attribute these results to stronger solvation layers in low MW PEG which keep contacts between particles lubricated even under high stress.

[1] N. James, E. Han, R. Lopez, J. Jure H Jaeger, “Interparticle hydrogen bonding can elicit shear jamming in dense suspensions”, Nature Materials volume 17, 965–970 (2018)
[2] E. Han, L. Zhao, N. Ha, S. Hseih, D. Szyld, H. Jaeger, “Dynamic jamming of dense suspensions under tilted impact”, Phys. Rev. Fluids 4, 063304 (2019)