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Two-step yielding in a jammed microgel suspension
Fayis Kanheerampockil1,2,3, Rachna Maria Kurian1, Gary Bryant3
1Polymer Science and Engineering Division CSIR-National Chemical Laboratory, Pune, Maharashtra 411008, India. sk.bhat.ncl@csir.res.in.
Soft Matter
|June 16, 2026
Summary
Soft core-shell microgels exhibit unique two-step yielding behavior in jammed states. This phenomenon, driven by particle softness and structure, involves distinct stages of deformation and flow under shear stress.
Area of Science:
- Soft Matter Physics
- Rheology
- Colloidal Science
Background:
- Colloidal glasses exhibit complex yielding behaviors under deformation.
- Understanding yielding mechanisms is crucial for material design and application.
Purpose of the Study:
- To elucidate the mechanism of two-step yielding in repulsive colloidal microgel glasses.
- To investigate the influence of particle softness and structure on yielding.
Main Methods:
- Shear deformation experiments including strain sweep and start-up flow.
- Creep-recovery tests and Lissajous-Bowditch curves to analyze nonlinearities.
- Systematic variation of microgel volume fraction and particle architecture.
Main Results:
- Two-step yielding was observed specifically in soft core-shell microgels within the jammed glass regime.
- Stiff core-shell and homogeneous microgels did not exhibit two-step yielding.
- Strain stiffening between yield points is attributed to interpenetrated polymer chain interlocking.
Conclusions:
- Softness and core-shell structure are essential for two-step yielding in microgel glasses.
- The yielding process involves resistance to cage breaking followed by macroscopic flow.
- Microgel deformation and compression play a key role in the observed rheological response.
