Date(s) - 04/17/2018
4:00 pm - 5:00 pm
Department of Materials Science and Engineering
Penn State University
James Runt is Professor of Polymer Science in the Materials Science and Engineering Department at Penn State University. He is the author of ~220 peer-reviewed publications and book chapters, and is a contributor on 8 patents on a cardiac assist device. His research group has been actively investigating the nanostructure – dynamics relationships in a broad range of polymeric materials, including ion-containing polymers; polymers for high temperature capacitor energy storage; and polyurethanes and polyureas (as blood-contacting materials and mitigation of blast/shock energy, respectively). He is a Fellow of the American Physical Society and the American Institute of Medical and Biological Engineers, and received the Wilson Research Award from Penn State in 2014. He served as a co-editor of the recent ACS Symposium Series book: Polymers for Energy Storage and Delivery: Polyelectrolytes for Batteries and Fuel Cells, and as an editor of the ACS Professional Reference Series book: Dielectric Spectroscopy of Polymeric Materials: Fundamentals and Applications.
“Dynamics from Broadband Dielectric Spectroscopy:
Non-Ionic and Ionic Polymers”
The focus of this presentation will be on the insight that broadband dielectric (impedance) spectroscopy (BDS) brings to our understanding of the dynamics of non-ionic and ionic polymers. An overview of two recent investigations will be presented. The first focuses on bio-based polyfarnesene (PF) and the first comprehensive investigation of the molecular weight dependence of the dynamics . Extended PF chain conformations arising from tightly packed C11/C13 pendant groups reduce the probability of chain entanglements and leads to Rouse-like melt dynamics up to a critical molecular weight ~ 105 g/mol. At higher molecular weights, PF behaves as an entangled polymer melt. BDS measurements establish PF as a type-A polymer, whose normal mode relaxation is strongly dependent on molecular weight, providing a compliment to melt rheology for exploration of PF global chain dynamics.
If time permits, the second portion will focus on charge transport in model ionomers when confined in unidirectional nanoporous silica membranes . These findings are relevant to reports of improved ion transport in nm length scale phase-separated polymer electrolytes. Under nm confinement in native pores, the macroscopic transport quantities are lower by about 1.4 decades compared to the bulk. This can be explained by considering the interfacial layer between the ionomer and the silica membrane surfaces. An enhancement in dc conductivity is observed however when the surfaces of the pores are treated with a non-polar organosilane. This effect becomes more pronounced at lower temperatures and is hypothesized to arise from slight changes in molecular packing caused by the 2D geometrical constraint.
 C. Iacob, T. Yoo, J. Runt, Submitted for publication.
 C. Iacob, J. Runt, ACS Macro. Lett. 5, 476 (2016).