When:
Thursday, January 31, 2019
4:00 PM - 5:00 PM CT
Where: Ryan Hall, Room 4003, 2190 Campus Drive, Evanston, IL 60208 map it
Audience: Faculty/Staff - Student - Public - Post Docs/Docs - Graduate Students
Cost: Free!
Contact:
Lindsay Haukebo
Group: International Institute for Nanotechnology
Category: Lectures & Meetings
Matthew Tirrell
Institute for Molecular Engineering
University of Chicago and Argonne National Laboratory
Polyelectrolytes in multivalent ionic media: New physics and new materials
Multivalent interactions in systems of polyelectrolytes can exhibit dramatic, non-monotonic effects, for example, switching forces from repulsive to attractive, and back to repulsive again, in some cases. The Tirrell Group has been studying these patterns of behavior with the surface forces apparatus (SFA) and with electrochemical methods, such as cyclic voltammetry, which enables the quantitative determination of the number of multivalent ions residing in thin layers of charged polymers. At fixed ionic strength, all cause strong shrinkage and condensation of poly(styrene sulfonate) brushes over a narrow range ratio of multivalent to monovalent ions. When the multivalent ion is an oppositely charged polymer, new fluid phases can form. The Tirrell Group has clarified the quantitative aspects of the phase diagram for a simplified polyelectrolyte complex system. Charged blocks in copolymers lead to materials with new types of ordered phases. Effects of these multi-valent interactions on supermolecular and biomolecular assembly will be discussed. There are many possibilities for the creation of new materials based on electrostatic assembly involving multivalent interactions.