Description:

Our first ChBE seminar of the Winter Quarter will be presented by two of our grad students, detailed information is given below:

Date & Time: Thursday, January 5th 9:00 am – 10:00 am

Location: Searle 1441 (refreshments will be available at 8:45am)

Speaker
Liz Dhulst, PhD Candidate, Torkelson Lab

Title
Phase-Separated Elastomers: Novel Syntheses and Characterization Techniques

Abstract 
Two-phase segmented polymers produce unique kinetic and thermodynamic challenges due to reaction-induced phase separation and incompatible segments. In the first section of my talk, novel two-phase hybrid materials are synthesized using thiol, epoxide and acrylate functionalized starting materials. Analysis of reaction kinetics shows that thiol-acrylate reactions are much faster than thiol-epoxy reactions; consequently, we have also developed a one-pot synthesis of thiol-acrylate-epoxy hybrid networks using room temperature reactions and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) as catalyst. Beyond good mechanical properties, some of the resulting phase-separated networks are very good shape memory polymers, with shape-fixity values above 95% and shape-recovery values above 99% after multiple cycles. Segmented polymers are two-phase materials and therefore, their properties are strongly influenced by the extent of phase separation. Next, we apply fluorescence for the first time to investigate the phase separation of segmented polyurethanes. Our novel use of intrinsic fluorescence takes advantage of the aromatic structure in the most common hard segments of polyurethanes in order to gain information about molecular alignment in thin film geometries. It was found that static excimer fluorescence is concentrated at the interfaces and the molecular orientation of aromatic rings is impacted by the polymer-substrate interactions.

Speaker
Shadid Askar, PhD candidate, Torkelson Lab

Title
Stress Relaxation and Stiffness in Thin Polymer Films and Nanocomposites: Characterization via Fluorescence Spectroscopy

Abstract
The miniaturization of technology often requires the use of device features with nanoscale dimensions. It has been well documented over the past two decades that confining polymers to such length scales causes deviations in the properties relative to bulk behavior. For instance, polymer properties such as glass transition temperature (Tg) and physical aging could change depending on the degree of confinement. While there is consensus among reports on Tg- and physical aging-confinement effects, general trends among reports of modulus- or stiffness-confinement behavior are less clear. A major goal of my thesis research is to investigate how various factors such as temperature, substrate stiffness, interfacial perturbations, thermal history, and others impact stiffness-confinement behavior in polymer films and nanocomposites. To this end, I have developed a novel fluorescence technique that provides a measurable sensitive to polymer stress and stiffness. This seminar will describe parts of my doctoral research on characterizing residual stress relaxation in supported polymer films as well as stiffness-confinement effects in films and nanocomposites. Results will be presented describing the first direct characterizations of stiffness gradient length scales near substrate and free-surface interfaces using a non-contact approach. By carefully considering the various factors impacting stiffness-confinement effects, general trends in such behavior can be identified which provides consensus among reported in the research community.

Description:

Alex Dowling

Title:
Multiscale Systems Engineering for Energy Technology Innovation

Growing worldwide energy demands and concerns for environmental impacts from energy conversion (e.g., CO2 emissions, water availability, air quality, etc.) are driving a paradigm shift in how the world thinks about energy. Creating sustainable energy technologies is an inherently multiscale problem, requiring innovations at the materials, devices, systems, and infrastructures length and timescales. Yet collaboration across these scales is often inhibited by complexity and domain specific models. New systems engineering approaches are needed to accelerate technology innovation by capturing the most important multiscale interactions and integrating expertise from many disciplines.

Part 1 of this seminar investigates the economic incentives for multiscale dynamic flexibility embedded in price signals from electricity markets (infrastructure). Technology specific economic assessment is posed as a large-scale optimization problem: manipulate the energy system control strategy (e.g., mass and energy flows, storage levels) and the market participation schedule in order to maximize revenue subject to system physics and operational limitations. Revenue potentials are estimated for two technologies, large-scale solar thermal electricity generation and utility-scale energy storage, using historical data from California for all of year 2015. Most striking, the analysis finds that a majority (over 60%) of the economic opportunities are available solely through real-time markets and ancillary services, which require fast flexibility (at 15-minute and shorter timescales) to monetize. In contrast, most previous techno-economic studies focus on slower timescales (hour resolutions). Our results indicate that such analyses are misleading, as they undervalue flexibility and economic potential. Moreover, these results highlight opportunities for new materials, devices, and energy systems that can provide fast flexibility.

Investing in energy infrastructures often involves many stakeholders with conflicting priorities for multiple social, technical, economic and environmental objectives. Part 2 of this seminar presents a decision-making framework to compute families of Pareto efficient compromise solutions. Coherent risk metrics are used to shape the distribution of stakeholder satisfactions and interpret the impact of individual stakeholder opinions. Through two applications, selection of combined heat and power conversion technologies to meet multi-energy demands for residential housing complexes and placing infrastructure to process organic waste, we demonstrate how the framework identifies perceptive compromises, helps resolve conflicts, and facilitates targeted negotiations. As energy infrastructures grow in complexity and interdependence, multi-stakeholder conflict resolution will become increasingly important.

Bio:

Alexander (Alex) Dowling is a postdoctoral fellow in the Department of Chemical and Biological Engineering at the University of Wisconsin-Madison working with Prof. Victor M. Zavala. He completed his PhD in Chemical Engineering at Carnegie Mellon University under the supervisor of Prof. Lorenz T. Biegler. Dr. Dowling’s research seeks to develop systems engineering approaches grounded in firsts principles mathematical modeling and large-scale nonlinear optimization to design and control a broad variety of energy technologies. Applications include advanced separations, electricity generation with CO2 capture, combined heat and power systems, electrochemical energy storage, and large-scale solar thermal energy harvesting. Dr. Dowling’s interest in systems engineering dates back to his undergraduate days, during which he raced twice as the Head Strategist of the University of Michigan Solar Car Team (North American Solar Challenge in 2008, World Solar Challenge (Australia) in 2009).

Description:

Linsey Seitz 

Title:
Developing Enhanced Catalysts for Electrocatalytic Water Oxidation Using Spectroscopic Insights

Renewable sources, such as wind and sun, supply more than enough energy to meet the increasing global demand and are promising solutions to shift our dependence away from fossil fuels as long as challenges with intermittency, scale, and cost effectiveness can be overcome. While recent developments have improved capture efficiencies for these sources, effective processes to convert and store this energy are needed. Chemical storage of energy using optimized catalytic reactions can produce high energy density fuels and commodity chemicals while allowing for spatiotemporal decoupling of the energy production and consumption processes. This talk will cover my recent work pursuing fundamental understanding of such catalytic reactions towards production of renewable fuels and chemicals. In addition, I will present a model for assessing practical efficiency limits for solar hydrogen production devices, as well as a water splitting device that achieves a record 30% solar-to-hydrogen efficiency.

Water oxidation, also known as the oxygen evolution reaction (OER), plays a key role in electrochemical processes such as water splitting and carbon dioxide reduction by providing the necessary protons and electrons to drive these reactions. Improving the efficiency and stability of OER catalysts can have a direct impact on device efficiency and cost effectiveness of renewable energy technologies. In this talk, I will discuss studies of controlled catalyst surfaces with an emphasis on determining intrinsic catalyst activity coupled with insights from advanced characterization techniques, such as x-ray absorption and x-ray emission spectroscopy, which are invaluable for investigating electronic, chemical, and geometric structure of materials. For example, using in situ x-ray absorption spectroscopy, changes in electronic structure for both manganese oxide and gold were investigated to understand why the combined catalyst material has an order of magnitude better activity than either catalyst alone. Furthermore, in collaboration with theory and by taking advantage of high-quality material growth techniques, a novel catalyst was developed that is stable in acid and outperforms known iridium oxide and ruthenium oxide systems, the only other OER catalysts that have reasonable activity in acidic electrolyte. Research at the interface of catalysis and spectroscopy towards developing a deeper understanding of these catalytic systems provides direction for further tuning of catalysts to develop the next generation of materials for renewable energy technologies.

Bio: 

Linsey Seitz received her B.S. (2010) in Chemical Engineering with a Biomedical Engineering Option from Michigan State University supported by an Alumni Distinguished Scholarship which covered full tuition, room and board, plus other expenses. During all four years of her undergraduate studies, she conducted research under the supervision of Professor Christina Chan. Additionally, she spent one summer as a visiting undergraduate researcher with the CPIMA program at University of California, Berkeley in Professor Susan Muller’s lab.

Linsey received her M.S. (2013) and PhD (2015) in Chemical Engineering from Stanford University under the guidance of Professor Thomas Jaramillo. Her PhD thesis entitled, “Developing Enhanced Mixed Metal Oxide Catalysts for Electrocatalytic Water Oxidation Using Insights from X-ray Absorption Spectroscopy,” features fundamental studies of electrochemical catalysts using a variety of synthesis and characterization techniques including both ex situ and in situ x-ray absorption spectroscopy conducted at the Stanford Synchrotron Radiation Lightsource. Her work resulted in 6 first author publications and 6 additional publications, all in peer-reviewed journals. During her graduate studies, Linsey was a National Science Foundation Graduate Research Fellow and a Stanford DARE Fellow; the latter is a fellowship program for advanced doctoral students who want to pursue academic careers and whose presence will help diversify the professoriate.

She is currently a postdoctoral fellow at the Karlsruhe Institute for Technology in Germany with the Applied Spectroscopy group of Dr. Lothar Weinhardt and Professor Clemens Heske. Her work techniques is funded by a Helmholtz Postdoctoral Fellowship and currently focuses on investigating adsorption of reactants and intermediates on zeolite catalysts for NOx selective catalytic reduction using in situ soft x-ray techniques.

Description:

Christian Pester 

Title: 
Engineering 2D and 3D polymer structures via external regulation

Polymer nano and microstructures play an important role for a plethora of applications. This presentation will provide two examples of how ordered polymer structures can be manufactured and studied on different length scales, both in bulk and thin films.
Electric fields are a convenient tool for the fabrication of ordered nanostructures because they can be applied instantly, localized precisely, and scale favorably with dimensions relevant to nanofabrication techniques. However, although polymeric materials are increasingly used in electronic applications, their physical behavior in the presence of electric fields is not well understood. This talk illustrates electric field-induced effects in diblock copolymers, including alignment, domain spacing alterations, order-disorder, and order-order transitions.
Defined polymer structures also have significant relevance in a variety of thin film applications. Accordingly, this presentation describes the design and application of a novel experimental setup to combine light-mediated polymerization and highly efficient ‘click’ chemistries in a stop-flow lithographic setup. This allows fabrication of hierarchical surface-grafted polymer brush architectures of previously unimaginable complexity to be readily accessed from uniformly functionalized substrates.

Bio:

Christian received his Diploma in Polymer and Colloidal Chemistry from the University of Bayreuth (Germany), before working for Prof. Alexander Böker at the DWI - Leibniz Institute for Interactive Materials (RWTH Aachen University, Germany). In 2013, he graduated summa cum laude and was awarded the Borcher’s Medal for his Ph.D. thesis on block copolymers in electric fields. He was then hosted by Prof. Edward J. Kramer at the University of California, Santa Barbara as an Alexander von Humboldt Fellow. Currently, working with Prof. Craig J. Hawker, Christian is engineering novel methods for topographical and chemical surface patterning with well-defined grafted polymer brush architectures.

Description:

Samanvaya Srivastava

Title:
Complexation Driven Self-Assembly of Block Copolyelectrolytes

Polyelectrolyte complexes (PEC) form when oppositely charged polyelectrolyte chains spontaneously associate and phase separate in aqueous media. Conjugating one or both the polyelectrolytes with neutral polymers restricts bulk phase separation of the PECs, and thus leads to self-assembled structures with PEC domains surrounded by neutral polymer coronae, forming micelles and hydrogels. The PEC domains in these assemblies can encapsulate hydrophilic cargo and have tremendous potential for biomedicine, chemical-sensing applications, food systems and cosmetics. This talk focuses on physical properties of model PEC hydrogel assemblies comprising oppositely charged block copolyelectrolytes. Created using a novel two-step synthesis scheme, the copolyelectrolytes self-assemble to form hydrogel structures with polyelectrolyte complex domains serving as physical crosslinks. Precise PEC domain size, morphology, spacing and ordering is achieved via tuning of the polymer architecture and loading, ideal for fundamental studies. Structural investigations employing complementary X-¬ray and neutron scattering elucidate the contributions of the charged and the neutral blocks in defining and directing the structure of these self-assemblies, respectively. Extending these ideas to assembly of model oppositely charged triblock copolyelectrolytes, we find that at low concentrations the materials spontaneously assemble into phase separated inter-connected networks of PEC cores, underscoring the disparity between complexation-driven assembly of triblock copolyelectrolytes and hydrophobicity driven assembly of their uncharged amphiphilic counterparts. Molecular dynamics simulations are employed to provide insights on the driving forces behind these unique assemblies and their relationships to corresponding assemblies of amphiphilic molecules.

Bio:

Samanvaya Srivastava is a postdoctoral scholar at The University of Chicago, where he is working with Prof. Matthew Tirrell on design, structure-properties relationships and applications of polyelectrolyte based self-assembled materials. He received his Ph. D. from Cornell University in Chemical and Biomolecular Engineering in 2014. His doctoral dissertation research under the supervision of Prof. Lynden A. Archer was focused on elucidating structure and properties of nanoparticle dispersions. Samanvaya developed strategies for achieving uniform nanoparticle dispersion in polymeric matrices and the effects of particle distribution on bulk properties in nanocomposites. Prior to this, he received his B. Tech. and M. Tech. degrees in Chemical Engineering from Indian Institute of Technology Kanpur. In his Masters research, conducted under the guidance of Prof. Ashutosh Sharma, he studied the role of physical heterogeneities on substrate surfaces as manifested in the electric force induced patterns in thin polymer films.