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Prof. Daniel Hallinan
November 2 @ 11:00 am - 12:00 pm
Affiliation: Florida State University
ABSTRACT: Our research is driven by the desire to understand how nanostructure impacts the structure and dynamics of polymers. We focus on two classes of single-component, nanostructured polymeric materials: block copolymers and polymer-grafted nanoparticles. We are interested in poly(ethylene oxide) (PEO), a remarkable polymer with low glass transition temperature that can dissociate alkali metal salts (such as those of lithium). PEO is also hydrophilic and selective to CO2 over other gases. When it is combined with a hydrophobic polymer in a high-molecular-weight block copolymer it forms strong, free-standing membranes that are of interest as lithium battery electrolytes. When it is grafted to a nanoparticle, the inherent free volume can be modified, which is interesting for gas/vapor separation membranes. Battery and membrane separation performance requires rapid, selective transport. Transport, in turn, is affected by the structure and dynamics of the polymeric material. Two of our most recent experimental results will be presented: (1) time-resolved X-ray scattering studies of a block copolymer composed of PEO and polystyrene (a glassy polymer that confers mechanical strength) and (2) detailed investigation of the structure and properties of gold nanoparticle (Au NP) monolayers. The first project uses X-ray photon correlation spectroscopy (XPCS), a time-resolved technique that can probe dynamics on nanometer length scales in polymer melts. In an attempt to understand the physical origin of the surprising dynamics observed with XPCS, we compare XPCS results with chain dynamics probed using small-amplitude oscillatory rheology. In the second project, we have developed a patented technique to deposit Au NPs in well-ordered monolayers. The spacing between NPs is dictated by the molecular weight of the ligands attached to the particle surfaces. Thus, particle spacing has been used to examine the conformations of grafted PEO chains in solvents of varying quality. In summary, two of our most recent studies will be presented that are part of our effort to understand how nanostructure affects the mesoscopic properties of polymeric materials. The eventual goal is to elucidate how mesoscopic properties are transmitted to the macroscopic scale which ultimately dictates the performance of polymer membranes in sustainable energy applications.
BIOGRPAHY: 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.