Description:

Hyomin Lee

Title:
Structure and Dynamics of Soft Matter at Interfaces: Films, Drops, and Beyond

The performance of functional materials is governed by their ability to interact with the surrounding environment in a well-defined and controllable manner. Whether it is selectively interacting with a biomolecule or a solute, or responding to pH or temperature, the environment-material interface is essential in determining the performance of materials in various applications. As manifested in multi-layered films and multi-phase emulsion drops, additional material interfaces and compartments provide the means to create composite materials where the surface and the bulk of the material can be independently engineered and controlled. This provides a new perspective in the design and fabrication of novel functional materials.
In this talk, I will begin by exploiting the ability to separately tune the surface and bulk properties of a nanostructured polymer thin film. We propose a new physical concept “zwitter-wettability”, whereby the film readily absorbs water vapor while simultaneously exhibiting hydrophobic character to liquid water. These mechanistic concepts and the quantitative morphological characterizations enabled us to design zwitter-wettable films with significantly enhanced antifog and even frost-resistant behavior.
In the second part of this talk, I will show how we utilize the precise flow control of multi-phasic fluids in droplet-based microfluidics to prepare novel functional materials that otherwise would have been inaccessible. For instance, we produced triple emulsion drops with an ultra-thin intermediate layer consisting of either hydrogel or fluorocarbon oil to successfully encapsulate a broad range of cargo materials with high loading efficiency. These emulsion drops have been demonstrated to exhibit interesting properties and great technological potential for encapsulation and controlled release of challenging and important active materials such as volatile small molecules and proteins in emulsion-templated microcapsules.

Bio:

Dr. Hyomin Lee is a postdoctoral researcher in David Weitz Laboratory at Harvard University. He received his B.S. in Chemical and Biological Engineering from Seoul National University (SNU), and his Ph.D. in Chemical Engineering from Massachusetts Institute of Technology (MIT) in 2014, under the guidance of Prof. Robert E. Cohen and Prof. Michael F. Rubner.

Description:

Praveen Bollini

Title:
Understanding and Controlling Rate Processes in Porous Materials:
From CO2 Separations to Hydrocarbons Conversion

Engineering the next generation of nanoporous materials will enable atom-efficient catalysis, and energy-efficient separations processes. This talk will focus on two studies where a molecular-level understanding of rate processes enables significant improvements in process performance. The first part of the talk will identify principal factors governing the kinetics of CO2 adsorption onto supported amine adsorbents for flue gas applications. Based on these factors, I will discuss strategies for designing adsorbents that simultaneously exhibit both high equilibrium adsorption capacities as well as rapid adsorption kinetics. The second part of this talk will illustrate the identity of key intermediates acting as either co-catalysts for product formation or precursors to catalyst deactivation in the conversion of methanol to olefins over zeolites. This understanding of key intermediates is then used to develop a hydrocarbon seeding strategy that enhances light-olefin yields while also mitigating carbon loss during methanol to olefins catalysis. These investigations serve as examples of how a molecular-level picture of physical and chemical processes can inform the development of advanced adsorbents, membranes, and catalytic materials.

Bio:
Praveen Bollini is originally from India, and received his Bachelor of Engineering (B.E.) in Chemical Engineering from the Institute of Chemical Technology, Mumbai, India in 2008 and a Ph.D. in Chemical Engineering from the Georgia Institute of Technology in 2013. He was a Research Engineer at the Dow Chemical Company in Freeport, TX from 2013-2015. He has been a postdoctoral scholar at the University of Minnesota since March 2015.

Description:

Michelle Calabrese

Title:
Developing structure-property relationships in soft materials via advanced rheological and neutron techniques

The design of soft materials with optimal flow properties is vital in applications ranging from polymer processing to drug delivery, where materials undergo steady and dynamic nonlinear deformations during processing, transport and use. Non-optimal flow conditions can lead to flow instabilities, metastable states, or phase separation in systems ranging from biological materials to colloids and polymers. Flow-small angle neutron scattering (flow-SANS) presents a unique opportunity to understand this non-trivial coupling between flow behavior, molecular topology and material performance by combining rheometry with time- and spatially-resolved SANS. In this talk, I will discuss innovative flow-SANS methods that link microstructure, macroscopic flow properties, and dynamics in a model system of surfactant wormlike micelles (WLMs). The unique ability of WLMs to branch, break, and reform under shear often leads to shear banding, a common flow instability of significant scientific interest. First, I will explain how flow-SANS can be adapted to determine complex mechanisms behind shear band formation. I will then experimentally validate constitutive modeling predictions of shear banding under dynamic deformation for the first time, based on microstructural responses to deformation. Finally, I will demonstrate the practical utility of these methods by developing quantitative metrics to predict dynamic shear banding from rheology and flow-induced orientation. Together, advanced rheological and neutron techniques provide a platform for creating structure-property relationships that predict flow and structural phenomena in self-assembled solutions and other soft materials.

Bio:

Michelle graduated from the University of Pennsylvania with a B.S.E. in chemical engineering in 2012. She is currently a fifth year chemical engineering PhD student at the University of Delaware, working with Norman J. Wagner. Michelle has spent the last 2.5 years of her thesis stationed permanently at the NIST Center for Neutron Research, and has routinely worked at the scattering facilities at the Institut Laue-Langevin (ILL) in Grenoble, France. Upon completing her PhD, she will start a postdoc at MIT in Bradley Olsen's group. Her research interests include developing and advancing techniques in neutron scattering and rheology to characterize soft materials, and using these techniques to design and develop novel soft matter systems.

Description:

Nirala Singh

Title:
Advances in Electrocatalysts for Flow Batteries and Renewable Fuels

Renewable energy sources provide an important pathway to counter increasing greenhouse gas emission related challenges. However, these sources are provided mostly in the form of intermittent electricity, which must be either stored until it is needed or converted into useful chemicals. In this talk, I will discuss two processes that can make use of renewable electricity: (i) electricity storage using a H2/Br2 flow battery and (ii) electrocatalytic hydrogenation (ECH) of waste biooil to form fuels. A challenge for both these processes is developing stable and active electrocatalysts to drive the desired reactions (hydrogen evolution and oxidation for the H2/Br2 flow battery, and hydrogenation of phenol as a sample ECH reaction). In this talk I will describe the approach we have taken to create new electrocatalysts for these specific applications and to lay the framework for creating new electrocatalysts for general applications in electrochemistry. For the H2/Br2 flow battery, because bromine and bromide poison metal electrocatalysts, we tested metal sulfides for hydrogen evolution and oxidation and showed they maintain stability even in the presence of bromine. We determined the active sites of the best performing metal sulfides (ex. by using thermal catalytic reactions to understand the role of hydrogen adsorption energy on electrocatalytic activity) and selectively synthesized these active sites to make improved electrocatalysts. This led to vastly improved electrocatalysts for the H2/Br2 flow battery, with continued improvement as synthesis techniques are optimized. For the electrocatalytic hydrogenation of phenol (a model of lignin-based biomass), by understanding the surface kinetics (through rate analysis and in situ characterization) and the role of hydrogen, we found new reaction conditions to prevent electrocatalyst deactivation at elevated temperatures and thus enable higher rates than previously achievable. Also, by tuning the hydrogen adsorption energy on metal surfaces via pH control, we showed that the catalyst’s activity can be increased. These results show how understanding surface catalysis and electrocatalysis can lead to development of improved materials, and provide new tools for renewable energy creation and use. 

Bio:

Nirala Singh is currently a Washington Research Foundation Innovation Fellow at the University of Washington conducting postdoctoral research on understanding electrocatalytic and thermal catalytic hydrogenation. He received his PhD in Chemical Engineering at the University of California, Santa Barbara. During his doctoral work he focused on developing electrocatalysts for H2/Br2 flow batteries, as well as research on artificial photosynthesis, wastewater oxidation and solar absorbers. His research goals include understanding surface electrocatalysis through synergistic electrochemical and thermal catalytic experiments, collaborating with theorists, and in situ catalyst characterization. These increases in fundamental understanding aim to improve existing sustainable electrochemical processes as well as provide guidance and pathways for new processes, in particular related to energy storage and generation.