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Multivalent Ionic Interactions in Multicomponent Polyelectrolyte Mixtures: From New Physics to New Materials

June 13, 2012 4:00PM to 5:00PM
Presenter 
Matthew Tirrell, The University of Chicago, Institute for Molecular Engineering
Location 
Building 440, Room A105-106
Type 
Colloquium
Series 
CNM Nanoscience Colloquium
Abstract:
Highly charged polymer chains in monovalent salt media exhibit a fairly simple range of behaviors, swelling in low salt, shrinking in high salt, based on the screening of repulsive electrostatic interactions among the segments. In the presence of other multivalent constituents, attractiveforces arise. These attractions produce strong collapse of polyelectrolyte chains, adhesion between polyelectrolyte bearing surfaces, precipitation, and in the case of mixtures of oppositely charged polyelectrolytes, formation of fluid complex coacervate phases. We have measured the attractive forces between layers of polyelectrolyte brushes immersed in multivalent ionic media as a function of ionic strength. We have characterized coacervate formation in mixtures of model polyelectrolytes. We demonstrate how coacervate formation can be used to create new self-assembled materials, such as physically crosslinked hydrogels.