CHBE Seminar: Dr. Pinar Akcora, Stevens Inst. of Technology
Friday, October 27, 2023
Room 2108 Chemical and Nuclear Engineering Building
Chain Dynamics and Mechanical Properties of Polymer Nanocomposites with Complex Interphases
Abstract: Miscible polymer blends with different glass transition temperatures (Tg) are known to form confined interphases between glassy and mobile chains. Our group investigates the dynamic asymmetry in polymer blends in the presence of nanoparticles. Thin interfacial layers of polymers, commonly known as immobile glassy layers, control the local and long-time chain relaxations at different length scales, providing unusual mechanical responses to polymer nanocomposites. We found that nanoparticles adsorbed with a high-Tg polymer, poly(methyl methacrylate), and dispersed in a low-Tg matrix polymer, poly(ethylene oxide), exhibited a liquid-to-solid transition at temperatures above Tg’s of both polymers. In this talk, I will present the mechanical responses of other polymer combinations with varying Tg differences and will discuss the role of chain rigidity, chain conformations and local viscosity around magnetic nanoparticles as they heat up by applying magnetic fields. The dynamic asymmetry in interphases is further explored to explain shear stiffening in linear-grafted and loop-grafted particle composites. Our results show that chain topologies on nanoparticles is critically important to control the mixing of chains. The compositional and dynamic heterogeneities of these complex interphases will be discussed through dynamic results from rheology and broadband dielectric spectroscopy. This remarkable and unusual behavior of polymer nanocomposites can be used for high temperature applications where mechanical integrity is critical for the performance of hybrid materials.
Bio: Pinar Akcora is an Associate Professor in the Chemical Engineering & Materials Science Department at Stevens. She received her Ph.D. in Chemical Engineering at the University of Maryland-College Park in 2005 and completed her post-doctoral work at Columbia University between 2005-2008. She joined University of Missouri-Columbia, Chemical Engineering as an assistant professor in 2008 and has moved to Stevens in 2010. She is the recipient of the 2010 NSF-CAREER award and has received several grants from NSF-DMR, -CMMI and ACS PRF. She currently serves as the coordinator of the Nanotechnology Graduate Program at Stevens.