Biographical Information:
Gary S. Grest is an American computational physicist at Sandia National Laboratories. He holds BSc, MS, and PhD degrees by the Louisiana State University. His interest is the theory and simulation of nanoscale phenomena. Since 1998 he has been a member of the technical staff of Sandia Laboratories, since 2009 an adjunct professor in department of chemistry, Clemson University and since 2013 a Distinguished Sandia National Laboratories Professor in the department of chemical and biological engineering, University of New Mexico. His contributions are related to the understanding of the kinetics of domain growth, amorphous glasses, disordered magnets, and polymer dynamics.Abstract:
Relaxation of Topological Constraints in Ring-Linear Polymer Blends
The topological constraints of no free ends force non-concatenated ring polymers in a melt to form compact loopy globular conformations. This closed-loop structure also enables rings to be threaded by linear polymers in ring/linear blends, which leads to several interesting rheological properties. Ring-linear blends can be more viscous than either of the individual components and have stress relaxation that transitions from a power law decay for large ring fractions to a plateau as the fraction of rings decreases. This emergent behavior arises since ring-linear blends can form long-lived topological constraints, as shown in Figure 1. For majority-linear blends, the relaxation rate of the topological constraints depends primarily on reptation of the linear polymer as the rings can relax only after the linear polymers, resulting in the diffusive time τd for rings of length NR blended with linear chains of length NL to scale as τd ∼ N_R^2 N_L^3.4. We show how the Gauss linking integral can be used to efficiently evaluate the relaxation of topological constraints in ring-linear polymer blends.Acknowledgements
This work was performed, in part, at the Center for Integrated Nanotechnologies, an Office of Science User Facility operated for the U.S. Department of Energy (DOE) Office of Science. Sandia National Laboratories is a multimission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International, Inc., for the U.S. DOE’s National Nuclear Security Administration under Contract No. DE-NA-0003525.