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Seminar Series 2018 – Daniel T. Hallinan Jr., Ph.D.
October 1 @ 4:05 pm - 5:00 pm
Daniel T. Hallinan Jr., Ph.D.
Department of Chemical and Biomedical Engineering FAMU-FSU College of Engineering
“Transient Processes in Nanostructured Soft Materials”
Soft materials, such as polymers, can potentially address energy sustainability challenges. For example, polymer electrolytes can improve the safety, energy density, and lifetime of lithium batteries. In addition, polymer membranes enable more energy-efficient gas separation, including capturing carbon dioxide from flue gas and removing water vapor from gas streams. In all these examples, transient processes determine how well a material performs, because ions/gas/vapor must be transported rapidly. The challenge is to enable high transport rates while satisfying other requirements. In lithium batteries, the electrolyte must adhere to electrodes but block electrons and lithium dendrites. Membranes must be selective to the gas/vapor of interest, i.e. flux of the desired species must be much higher than that of the other species present, while also being strong enough to sustain applied pressure. Designing a homogeneous material that is strong, selective, and sticky is essentially impossible. However, nanostructure can confer seemingly incompatible macroscopic properties such as these. From studies of homogeneous polymers, it is known that these macroscopic properties are coupled to microscopic material behavior. Our group’s goal is to apply cutting-edge experimental techniques to better understand the physics of how nanostructure impacts microscopic polymer properties and how these properties are transmitted to the macroscopic scale. Much of our focus is on poly(ethylene oxide) (PEO) an interesting polymer that can conduct ions and is selective to carbon dioxide and water over other gases. This seminar will focus on time-resolved scattering and spectroscopic studies of a block copolymer composed of PEO and polystyrene (PS, a glassy polymer that confers mechanical strength). Block copolymers (BCPs) microphaseseparate into predictable nanostructures that are determined by chain length. We are interested in strongly microphaseseparated BCPs that form sharp interfaces between the PS and PEO phases. We have examined the role of interfacial tethering on PEO chain dynamics using neutron spin echo of selectively deuterated PS-PEO. We have also taken advantage of a recently developed technique, X-ray photon correlation spectroscopy (XPCS), that can probe dynamics on nanometer length scales in polymer melts. XPCS has enabled us to examine mesoscopic dynamics of BCP grains (groups of coherently oriented domains). Finally, time-resolved infrared spectroscopy has allowed us to measure transport of lithium salt and water in PS-PEO membranes. In conjunction with rheology, these experiments provide some insight into how nanostructure impacts microscopic, mesoscopic, and macroscopic properties.
Dr. Daniel T. Hallinan Jr. is an Assistant Professor at Florida State University with interest in fundamental polymer physics of nanostructured materials such as block copolymers and polymer-grafted nanoparticles as well as applications related to energy sustainability. He is a chemical engineer with bachelor’s degrees from Lafayette College and a PhD from Drexel University. His post-doctoral research was conducted at Lawrence Berkeley National Lab and the University of California, Berkeley. He is actively involved in the polymer communities of the American Physical Society and the American Institute of Chemical Engineers. He recently received an NSF CAREER Award, and has testified before a U.S. Congressional Subcommittee in support of national synchrotron facilities, which his group uses extensively.
MONDAY, October 1, 2018
4:05 pm| 201 NEB