Dept. Colloquium: Matthew Tirrell, Institute for Molecular Engineering, University of Chicago
Multivalent Ionic Interactions in Multicomponent Polyelectrolyte Mixtures: From New Physics to New Materials
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, attractive forces 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.