The Role of Hydrogen Bridging Bonds in the Shear-Thickening and Jamming of Dense Suspensions

TL;DR

This study investigates how hydrogen bonding in solvents influences shear thickening and jamming in dense suspensions, revealing a transition from shear thickening to shear thinning with larger solvent molecules.

Contribution

It demonstrates how molecular structure of solvents modulates frictional interactions and suspension rheology, providing a new way to control shear thickening behavior.

Findings

Transition from shear thickening to shear thinning with larger solvent molecules

Hydrogen bonding enhances frictional interactions at particle contacts

Molecular structure of solvent affects suspension rheology

Abstract

Strong shear thickening and jamming in dense suspensions are driven by friction as particles are sheared into contact. Control over these frictional interactions can be achieved via particle shape and roughness, and also via the particles' surface chemistry and interactions with the surrounding solvent. We report on experiments with cornstarch suspensions where friction is enhanced by molecular bridging when hydrogen atoms at the ends of solvent molecules bond with hydroxyl groups on the surfaces of adjacent particles. We systematically vary the hydrogen bonding propensity by increasing the size of the backbone of the solvent molecule, from water to diols with up to 4 carbon atoms. For a fixed particle weight fraction, we find a sudden transition from strong shear thickening (in water and ethylene glycol) to shear thinning (in propanediol and butanediol). Combining data from rheology, density functional theory simulations, and fixed-rate pull tests, our results show how changes in the solvent's molecular structure affect both particle-solvent and solvent-solvent interactions, and how this can be used to tailor the shear thickening and jamming behavior of suspensions.