Northwestern University

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Feb
22
Thu 8:45 AM

ChBE Seminar Series, Dr. Jeffrey J. Richards

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When: Thursday, February 22, 2018
8:45 AM - 10:00 AM  

Where: Technological Institute, L361, 2145 Sheridan Road, Evanston, IL 60208 map it

Audience: - Faculty/Staff - Student - Post Docs/Docs - Graduate Students

Contact: Cody Jarrett   847.467.4824

Group: McCormick-Chemical and Biological Engineering

Category: Academic

Description:

Jeffrey J. Richards

Title:
Colloidal Fluids as Electrical Current Collectors

Advances in synthetic techniques have enabled a revolution in the design of colloidal dispersions that contain particles with an enormous variety of sizes, shapes and compositions. These advances have not only provided access to a sophisticated understanding of intimate link between a dispersion’s microstructure and its macroscopic properties, but also form the basis of a powerful design paradigm to formulate advanced colloidal materials to address a wide range of important societal problems.


In this talk, I will highlight our recent progress toward understanding the intrinsic link between the electrical conductivity and the rheological properties of suspensions of electrochemically active nanoparticles. Such suspensions increasingly comprise the working fluid in electrochemical flow applications. In this context, a key design constraint collector is the trade-off between electrical performance and viscosity. To examine the origin of these macroscopic properties, we formulated suspensions of two, high-structured carbon blacks in neat propylene carbonate and characterize their rheological and electrical properties using small amplitude oscillatory shear and impedance spectroscopy at concentrations spanning the fluid-gel transition. Using these methods, we identify the electrical and mechanical percolation transitions and rationalize these results in the context of the equilibrium microstructure determined from scattering measurements. These results coupled with emerging in situ characterization techniques reveal a pathway toward current collectors with improved performance.

 

Bio:
Jeffrey J. Richards received his PhD in August 2014 from the Department of Chemical Engineering at the University of Washington working for Dr. Lilo D. Pozzo. During that time, he was an NSF IGERT Fellow and the College of Engineering Dean’s Fellow. After graduating from UW, he had the opportunity to join Dr. Norman Wagner’s group at the University of Delaware as a postdoctoral scholar in the Department of Biomolecular and Chemical Engineering Department before starting his NRC Fellowship at the NIST Center for Neutron Research in Gaithersburg, MD. Jeffrey’s current research focus at the NCNR is the development of in situ characterization techniques for electrochemically active colloidal systems.

 

 

Mar
1
Thu 8:45 AM

ChBE Seminar Series, Dr. Amanda Marciel

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When: Thursday, March 1, 2018
8:45 AM - 10:00 AM  

Where: Technological Institute, L361, 2145 Sheridan Road, Evanston, IL 60208 map it

Audience: - Faculty/Staff - Student - Post Docs/Docs - Graduate Students

Contact: Cody Jarrett   847.467.4824

Group: McCormick-Chemical and Biological Engineering

Category: Academic

Description:

Amanda Marciel

Title:
Structure and Rheology of Polyelectrolyte Complex Coacervates

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.

 

Mar
8
Thu 8:45 AM

ChBE Seminar Series

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When: Thursday, March 8, 2018
8:45 AM - 10:00 AM  

Where: Technological Institute, L361, 2145 Sheridan Road, Evanston, IL 60208 map it

Audience: - Faculty/Staff - Student - Post Docs/Docs - Graduate Students

Contact: Cody Jarrett   847.467.4824

Group: McCormick-Chemical and Biological Engineering

Category: Academic

Description:

TBA

Title:
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Bio:
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Mar
15
Thu 8:45 AM

ChBE Seminar Series

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When: Thursday, March 15, 2018
8:45 AM - 10:00 AM  

Where: Technological Institute, L361, 2145 Sheridan Road, Evanston, IL 60208 map it

Audience: - Faculty/Staff - Student - Post Docs/Docs - Graduate Students

Contact: Cody Jarrett   847.467.4824

Group: McCormick-Chemical and Biological Engineering

Category: Academic

Description:

TBA

Title:
TBA

 

Bio:
TBA