Unless otherwise noted, all seminars are held on Wednesdays in the College of Computing Building (Room 016) at 3 p.m. Refreshments are served at 2:30 p.m. outside Room 016.

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Dr. Amanda Marciel, The Institute for Molecular Engineering, The University of Chicago

“Structure and Rheology of Polyelectrolyte Complex Coacervates”

ABSTRACT

Polyelectrolyte complexes are highly tunable materials that span from low-viscosity liquids (coacervates) to high-modulus solids with high water content, making them attractive as surface coating, membrane purification and bioadhesive materials. However, most of their properties and their effects with salt, pH, polymer ratio and temperature have only been qualitatively described. Here, we present a scattering investigation of the structure and chain conformations, and rheological properties of polyelectrolyte complex (PEC) coacervates comprising model polyelectrolytes. Systematic studies using small-angle X-ray scattering (SAXS) of the structure and chain behavior in liquid PEC coacervates revealed a physical description of these materials as strongly screened semidilute solutions of polyelectrolytes comprising oppositely charged chains. At the same time, solid PECs were found to be composed of hydrogen-bonding driven stiff ladder-like structures with large correlation lengths. While the liquid complexes behaved akin to semidilute polyelectrolyte solutions upon addition of salt, the solids were largely unaffected by it. Terminal relaxations of the chains in PEC coacervates were explored by rheology measurements. Excellent superposition of the dynamic moduli data was achieved by a time-salt superposition, although with the shift factors varying more strongly than previously reported with increasing salt concentration.

BIO

Amanda Marciel is currently a postdoctoral fellow at the Institute for Molecular Engineering (IME) at The University of Chicago working with Professor Matthew Tirrell studying the physical properties of polyelectrolyte complexes. In 2015, Amanda completed her PhD with Professor Charles Schroeder at the University of Illinois at Urbana-Champaign where she developed a synthetic platform to precisely control polymer microstructure and implemented a microfluidic strategy to drive assembly of complex polymer architectures for biomedical and electronics applications.