Levich Institute Seminar Announcement, 09/20/2011
Steinman Hall, Room #312
(Chemical Engineering Conference Room)
Dr. Jon Halverson
Center for Functional Nanomaterials at Brookhaven National Laboratory
"Rheology of Ring Polymer Melts "
Ring polymers are of great interest not only because mitochondrial and plasmid DNA are usually cyclic, but mostly because rings represent the simplest model system where reptation or the snake-like motion typical of linear chains is completely suppressed. This suppression causes the topological constraints to dominate both the static and dynamic properties of the rings. While the behavior of entangled linear chains is well-described by the reptation theory of de Gennes and Edwards, a molecular theory for the dynamics of ring polymers has yet to be formulated. Toward this aim we have conducted equilibrium and non-equilibrium molecular dynamics simulations using a semiflexible bead-spring model to investigate the structure, dynamics and rheology of melts of nonconcatenated rings. The ring melts were found to diffuse faster than their linear counterparts and the zero-shear viscosity was found to scale as the chain length to the 1.4 power which is much weaker than the 3.4 power of linear chains. When a small number of linear contaminants are added to the rings the viscosity of the system rapidly increases.
BRIEF ACADEMIC/EMPLOYMENT HISTORY
Since July 2011 I have been a postdoctoral researcher working with Alexei Tkachenko in the Center for Functional Nanomaterials at Brookhaven National Laboratory. From 2008-2011 I worked as a postdoc in the Theory Group of Kurt Kremer at the Max Planck Institute for Polymer Research in Mainz, Germany. My education in chemical engineering took place at the City University of New York (Ph.D., 2008), University of Wisconsin (M.S., 2002) and University of Massachusetts (B.S., 2000).
RECENT RESEARCH INTERESTS: