02/16/17 - 9:45 AM to 11:00 AM
Professor Christopher Ellison
"Manipulating Polymers with Light-based Chemistries for Patterning Films and Fabricating Fibers"
Light activated chemistries are powerful for controlling the structure and function of polymers with spatiotemporal control without the need for contacting the sample. Here recent research will be described from two projects where light is employed to enable new polymer processing capabilities. First, a non-contact strategy for high-speed patterning of arbitrary shapes in polymer films will be described. In this approach, a topographical pattern can be preprogrammed and photochemically stored in a flat solid film. The topography is later revealed by simple thermal annealing without use of a wet or dry etch step, unlike traditional photoresist methods. It will also be shown that the mechanism for this process is rooted in the Marangoni effect that can induce flow of polymer melts driven by patterned surface energy gradients. The second project seeks to address the fact that fibers have been manufactured for decades using solvents or heat to reduce the viscosity of polymers and promote drawing. However, nature has engineered spiders and silkworms with benign ways of making silk fibers with high strength and toughness. Their approach of chemically linking small functional units (i.e., proteins) into long chain molecules and solid fibrillar structures is fundamentally different from current synthetic fiber manufacturing methods, where extrusion of pre-formed long chain polymers is facilitated with organic solvents or heat. Drawing inspiration from nature, a method will be described that uses light to trigger a thiol-ene photopolymerization to rapidly transform reactive liquid mixtures into solid thread-like structures as they are forced out of a capillary at high speeds. Besides being manufactured without using solvents/volatile components or heat, these fibers are mechanically robust and have excellent chemical and thermal stability due to their crosslinked nature.
Christopher J. Ellison
Christopher J. Ellison is an associate professor and the Piercy Professor of the Department of Chemical Engineering and Materials Science at the University of Minnesota. From 2008-2016, he was a faculty member in the McKetta Department of Chemical Engineering at the University of Texas at Austin where he was also affiliated with the Texas Materials Institute and the Materials Science and Engineering program. He earned a Bachelor of Science degree in Chemical Engineering from Iowa State University in 2000. He received his doctorate in Chemical Engineering from Northwestern University in 2005 where he studied physical aging and the glass transition in nanoconfined polymer thin films. From 2006-2008, he conducted post-doctoral research in the Department of Chemical Engineering and Materials Science at the University of Minnesota where he studied the phase behavior of polydisperse block copolymers and nanofiber manufacturing methods. He is recipient of numerous awards including the National Science Foundation's CAREER Award, DuPont Young Professor Award, the 3M Nontenured Faculty Award, the AIChE Owens Corning Early Career Award and the Norman Hackerman Award in Chemical Research from the Welch Foundation.
His group’s current research interests include structure, dynamics and processing of micro- and nano-structured polymers, light-activated chemistries for thin film patterning and fiber manufacturing and engineering bioinspired/bioderived materials. The direction of his research is motivated by a combination of fundamental and practical implications. Several central research themes include manipulating polymers with light for micropatterning or modulating physical properties (e.g., by photopolymerizations or reversible light activated reactions), exploiting and understanding structure or molecular dynamics arising from confining polymers to the nanoscale, engineering bioinspired/bioderived materials or materials processes and sub-20 nm lithography using self-assembled thin film polymer templates. An important aspect of Ellison's laboratory is the use of well-established synthetic chemistries (anionic and controlled free-radical polymerization, basic monomer synthesis, etc.) to control all aspects of molecular architecture. This critical framework is required for establishing quantitative relationships in complex multi-scale materials. His group also works closely with other research groups focused on theory and simulation to both guide and advance its understanding of the experiments when appropriate.
Event DetailsLocation: 331 Smith HallHost: Professor Philippe Buhlmann