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Physical Society ColloquiumInterview for Faculty PositionViscoelasticity and Structural Aging in Colloidal PastesMaria KilfoilHarvardI will discuss the behavior of the dynamics of colloidal particles with a weak attractive interparticle interaction that is induced through the addition of polymer to the solvent. I focus on a discussion of aging of the solid gels formed by these colloid-polymer mixtures. They exhibit a delayed collapse induced by gravity. An intriguing feature of this behavior is the delay; the particles initially form a stress-bearing network that is stable under gravity for an extended time, and then it rather suddenly collapses. This is one form of aging of the sample. The collapse occurs on a characteristic time scale determined by the components of the system. The time evolution of the height of the sediment exhibits an unexpected scaling behavior, suggesting a universal nature to this delayed collapse. I will discuss how the viscoelasticity of the background fluid affects the behavior of the colloidal gel. I complement these measurements of the scaling of the collapse with microscopic investigations of the evolution of the structure of the network using confocal microscopy. These results provide new insight into the origin of this aging behavior.
Monday, March 10th 2003, 16:00
Ernest Rutherford Physics Building, R.E. Bell Conference Room (room 103) |