Abstract
Suspensions of multiarm star polymers are studied as models for soft colloidal glasses. Using an established pre-shearing protocol which ensures a reproducible initial state (the "rejuvenation" of the system), we report here the time evolution of the stress upon startup of simple shear flow for a range of shear rates. We show the existence of critical shear rates, γ c(c) which are functions of the concentration, c. When the suspensions are sheared at rates below γ c(c), the stress rises to a common value σc(c) which is also a function of the concentration. The system thus develops a yield stress. This behavior manifests itself as an evolution from a monotonic slightly shear-thinning flow curve to a flow curve dominated by a stress plateau. We relate this bulk evolution to spatially resolved velocity profiles. Hence, yield stress is linked to shear banding in this class of soft colloids.
Original language | English (US) |
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Pages (from-to) | 133-158 |
Number of pages | 26 |
Journal | Journal of Rheology |
Volume | 54 |
Issue number | 1 |
DOIs | |
State | Published - 2010 |
Externally published | Yes |
Keywords
- Aging
- Colloidal glass
- Shear banding
- Star polymer
- Stress relaxation
- Stress startup
ASJC Scopus subject areas
- General Materials Science
- Condensed Matter Physics
- Mechanics of Materials
- Mechanical Engineering