Northwestern University

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Oct
26
Thu 9:00 AM

Weekly ChBE Seminar Series

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When: Thursday, October 26, 2017
9:00 AM - 10:00 AM  

Where: Technological Institute, M345, 2145 Sheridan Road, Evanston, IL 60208 map it

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

Cost: Free

Contact: Elizabeth Rentfro   1.847.491.2773

Group: McCormick-Chemical and Biological Engineering

Category: Academic

Description:

Weekly talks given by guests or students of the Chemical and Biological Engineering Department. 

9AM Tech M345 (Refreshments served at 8:45)

Nov
9
Thu 9:00 AM

Weekly ChBE Seminar Series (Tim Lodge)

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When: Thursday, November 9, 2017
9:00 AM - 10:00 AM  

Where: Technological Institute, M345, 2145 Sheridan Road, Evanston, IL 60208 map it

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

Cost: Free

Contact: Elizabeth Rentfro   847.491.2773

Group: McCormick-Chemical and Biological Engineering

Category: Academic

Description:

Title: The Dynamics of Chain Exchange in Block Copolymer Micelles

Abstract: Block copolymers provide a remarkably versatile platform for achieving desired nanostructures by self-assembly, with lengthscales ranging from a few nanometers up to several hundred nanometers. In particular, block copolymer micelles in selective solvents are of great interest across a range of technologies, including drug delivery, imaging, catalysis, lubrication, and extraction. While block copolymers generally adopt the morphologies familiar in small molecule surfactants and lipids (i.e., spherical micelles, worm-like micelles, and vesicles), one key difference is that polymeric micelles are typically not at equilibrium. The primary reason is the large number of repeat units in the insoluble block, Ncore, which makes the thermodynamic penalty for extracting a single chain (“unimer exchange”) substantial. As a consequence, the critical micelle concentration (CMC) is rarely accessed experimentally; however, in the proximity of a critical micelle temperature (CMT), equilibration is possible. We use time-resolved small angle neutron scattering (TR-SANS) to obtain a detailed picture of the mechanisms and time scales for chain exchange, for systems at or near equilibrium. One model system is poly(styrene-b-(ethylene-alt-propylene)) (PS-PEP), in the PEP-selective solvent squalane (C30H62). Equivalent micelles with either normal (hPS) or perdeuterated (dPS) cores are initially mixed in a blend of isotopically substituted squalane, designed to contrast-match a 50:50 hPS:dPS core. Samples are then annealed at a target temperature, and chain exchange is revealed quantitatively by the temporal decay in scattered intensity. A second system consists of poly(n-butyl methacrylate)-b-poly(methyl methacrylate) in immidazolium-based ionic liquids. The dependence of the rate of exchange on all the key variables – concentration, temperature, Ncore, Ncorona, and chain architecture (diblock versus triblock) – will be discussed. 

Tim Lodge graduated from Harvard in 1975 with a B.A. cum laude in Applied Mathematics. He completed his PhD in Chemistry at the University of Wisconsin in 1980, and then spent 20 months as a National Research Council Postdoctoral Fellow at NIST. Since 1982 he has been on the Chemistry faculty at Minnesota, and in 1995 he also became a Professor of Chemical Engineering & Materials Science. In 2013 he was named a Regents Professor, the University’s highest academic rank.

In 1994 he was named a Fellow of the American Physical Society (APS). He received the Arthur K. Doolittle Award from the PMSE Division of the American Chemical Society (ACS) in 1998, and in 2004 he received the APS Polymer Physics Prize. He was elected to Fellowship in the American Association for the Advancement of Science, and he received the International Scientist Award from the Society of Polymer Science, Japan, in 2009. He was the recipient of the 2010 Prize in Polymer Chemistry from the ACS, and was also elected an ACS Fellow in 2010. In 2012 he received the Minnesota Award from the Minnesota Section of the ACS, and the Postbaccalaureate, Graduate and Professional Education Award from the University of Minnesota. He was honored with the Hermann Mark Award of the ACS Division of Polymer Chemistry in 2015, and in 2016 he was elected to the American Academy of Arts and Sciences.

Since 2001 he has been the Editor of the ACS journal Macromolecules. In 2011 he became the founding Editor for ACS Macro Letters. He has served as Chair of the Division of Polymer Physics, APS (1997–8), and as Chair of the Gordon Research Conferences on Colloidal, Macromolecular and Polyelectrolyte Solutions (1998) and Polymer Physics (2000). Since 2005 he has been Director of the NSF-supported Materials Research Science & Engineering Center at Minnesota. He has authored or co-authored over 400 papers in the field of polymer science, and advised or co-advised over 70 PhD students. His research interests center on the structure and dynamics of polymer liquids, including solutions, melts, blends, and block copolymers, with particular emphases on self-assembling systems using rheological, scattering and microscopy techniques.

Nov
16
Thu 9:00 AM

Weekly ChBE Seminar Series (Sossina Haile)

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When: Thursday, November 16, 2017
9:00 AM - 10:00 AM  

Where: Technological Institute, M345, 2145 Sheridan Road, Evanston, IL 60208 map it

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

Cost: Free

Contact: Elizabeth Rentfro   847.491.2773

Group: McCormick-Chemical and Biological Engineering

Co-Sponsor(s):
ISEN private

Category: Academic

Description:

Title: Extracting Material Properties from Relaxation Experiments

Abstract: Redox active oxides, with mixed ionic and electronic conductivity (MIEC), are critical components in a wide range of energy technologies, serving as electrodes in fuel cells and batteries, and as reactive substrates in solar-driven thermochemical reactors. Accurate knowledge of the surface reaction rate constant, , is essential for both optimal design of components using existing materials and rational discovery of new materials with enhanced catalytic activity. A variety of relaxation methods have been used extensively to determine . Such approaches rely on the change in some measurable property, most commonly conductivity, upon application of a step change in gas-phase oxygen partial pressure. Under the appropriate experimental conditions, the rate at which the property changes in response to the change in gas-phase oxygen chemical potential provides a direct measure of the material kinetic parameters. Here, we present several considerations relevant to accurate extraction of these parameters, with particular focus on identifying relaxation occurring due to thermodynamic rather than material kinetic reasons. Furthermore, while the electrical conductivity relaxation (ECR) method is one of the most widely employed relaxation techniques because of the ease with which high precision conductivity measurements can be made using samples of almost arbitrary dimensions, ECR is impractical for the evaluation of a material in which the change in conductivity in response to change in oxygen partial pressure is extremely small. For such materials mass relaxation emerges as a viable alternative measurement approach. To this end, we describe a high temperature mass relaxation apparatus based on a gallium phosphate piezocrystal microbalance that enables measurements at temperatures as high 700 °C.

Sossina M. Haile is the Walter P. Murphy Professor of Materials Science and Engineering at Northwestern University, a position she assumed in 2015 after serving 18 years on the faculty at the California Institute of Technology. She earned her Ph.D. in Materials Science and Engineering from the Massachusetts Institute of Technology in 1992. Haile’s research broadly encompasses solid state ionic materials and electrochemical devices, with particular focus on energy technologies. She has established a new class of fuel cells with record performance for clean and efficient electricity generation, and created new avenues for harnessing sunlight to meet rising energy demands. She has published more than 160 articles and holds 12 patents on these and other topics. Amongst her many awards, in 2008 Haile received an American Competitiveness and Innovation (ACI) Fellowship from the U.S. National Science Foundation in recognition of “her timely and transformative research in the energy field and her dedication to inclusive mentoring, education and outreach across many levels.”

Nov
30
Thu 9:00 AM

Weekly ChBE Seminar Series (Michael Wong)

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When: Thursday, November 30, 2017
9:00 AM - 10:00 AM  

Where: Technological Institute, M345, 2145 Sheridan Road, Evanston, IL 60208 map it

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

Cost: Free

Contact: Elizabeth Rentfro   847.491.2773

Group: McCormick-Chemical and Biological Engineering

Category: Academic

Description:

Weekly talks given by guests or students of the Chemical and Biological Engineering Department. 

9AM Tech M345 (Refreshments served at 8:45)