Tuning Interparticle Hydrogen Bonding in Shear-Jamming Suspensions: Kinetic Effects and Consequences for Tribology and Rheology

TL;DR

This study investigates how hydrogen bonding influences shear jamming in suspensions, revealing that urea reduces adhesion and friction, thereby shifting the shear-jamming point and advancing understanding of chemical effects on suspension rheology.

Contribution

It provides new insights into how molecular-scale hydrogen bonding and its modulation affect shear jamming through combined microscopy, NMR, and rheological studies.

Findings

Urea reduces interparticle adhesion and friction.

Time-dependent urea sorption shifts shear jamming onset.

Chemical control of hydrogen bonding influences suspension rheology.

Abstract

The shear-jamming of dense suspensions can be strongly affected by molecular-scale interactions between particles, e.g. by chemically controlling their propensity for hydrogen bonding. However, hydrogen bonding not only enhances interparticle friction, a critical parameter for shear jamming, but also introduces (reversible) adhesion, whose interplay with friction in shear-jamming systems has so far remained unclear. Here, we present atomic force microscopy studies to assess interparticle adhesion, its relationship to friction, and how these attributes are influenced by urea, a molecule that interferes with hydrogen bonding. We characterize the kinetics of this process with nuclear magnetic resonance, relating it to the time dependence of the macroscopic flow behavior with rheological measurements. We find that time-dependent urea sorption reduces friction and adhesion, causing a shift in the shear-jamming onset. These results extend our mechanistic understanding of chemical effects on the nature of shear jamming, promising new avenues for fundamental studies and applications alike.