Polyelectrolyte scaling laws for microgel yielding near jamming

Area of Science:

• Soft matter physics
• Polymer physics
• Rheology

Background:

• Microgels are widely used in industry and research for rheology control and studying jamming phenomena.
• While macro- and particle-scale behaviors are understood, the link between microgel yielding and polymer physics at low packing fractions remains unclear.

Purpose of the Study:

• To investigate if fundamental polymer physics scaling laws can predict the macroscopic yielding behaviors of packed microgels.
• To establish a connection between constituent polymer chain dynamics and microgel rheological properties near the jamming transition.

Main Methods:

• Experimental measurement of yield stress and cross-over shear-rate for anionic microgel systems.
• Preparation of microgels at packing fractions just above the jamming transition.
• Analysis using classic polyelectrolyte physics scaling laws.

Main Results:

• The measured yield stress and cross-over shear-rate data were successfully predicted by polyelectrolyte physics scaling laws.
• Diffusive relaxations of microgel deformation were found to predict the shear-rate at which yielding occurs.
• Elastic stresses from particle deformations accurately predicted the yield stress.

Conclusions:

• Basic polymer physics scaling laws are sufficient to predict macroscopic yielding behaviors in packed microgels near jamming.
• Microgel yielding phenomena are directly linked to the underlying polymer chain dynamics and deformations.
• This work bridges the gap between particle-scale physics and macroscopic rheological properties.