Paper Number
SC2
Session
Suspensions and Colloids
Title
Enhanced linear viscoelasticity of rough colloids
Presentation Date and Time
October 10, 2022 (Monday) 10:10
Track / Room
Track 1 / Sheraton 4
Authors
- Hsiao, Lilian (North Carolina State University, Chemical and Biomolecular Engineering)
- Pradeep, Shravan (University of Pennsylvania, Earth and Environmental Sciences)
Author and Affiliation Lines
Lilian Hsiao and Shravan Pradeep
Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC 27606
Speaker / Presenter
Hsiao, Lilian
Keywords
experimental methods; colloids; suspensions
Text of Abstract
The linear viscoelasticity of model colloids with tunable surface roughness is orders of magnitude higher than that of smooth hard spheres. We use sterically stabilized poly methyl methacrylate colloids suspended in squalene at high volume fractions to provide hard particle interactions and refractive index matching. To understand the linear viscoelastic measurements, we use a combination of mode-coupling theory, hydrodynamic modeling, and activated hopping theory to show that rough particles with significantly reduced localization lengths become trapped in their glassy cages for extended periods of time as compared to hard spheres. High-frequency data show that rough colloids, but not smooth colloids, display a transition from a free-draining to a fully lubricated state above the crossover volume fraction, and furthermore exhibit glassy and gel-like behavior. Scaling analyses support the idea that lubrication forces between interlocking asperities are enhanced, leading to rotational constraints and stress-bearing structures that significantly elevate the viscoelasticity of dense suspensions. The results provide a framework for how particle surface topology affects the linear rheology in applications such as coatings, cement, consumer products, and shock-absorbing materials.