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ChE Seminar – “Single Polymer Dynamics of Architecturally Complex Materials: Entangled Solutions, Combs, and Bottlebrush Polymers” by Dr. Charles Schroeder (University of Illinois at Urbana–Champaign)
October 24 @ 3:30 pm - 4:30 pm
Host: by Dr. Thomas Truskett
In this talk, I will discuss recent work from my group that effectively extends the field of single polymer dynamics to new materials, including polymers with complex topologies including rings, combs, and bottlebrush polymers. In the first part of the talk, polymer dynamics in semi-dilute unentangled and entangled DNA solutions are studied in extensional flow using single molecule techniques. Semi-dilute polymer solutions are commonly encountered in printing applications for organic electronics, yet despite recent progress, we still lack a complete understanding of these systems. Interestingly, we observe a unique set of polymer chain conformations indicative of flow-induced topological entanglements in solutions that are nominally unentangled at equilibrium. Our results also show a decrease in transient polymer stretch compared to dilute solutions. Single molecule experiments are directly compared to large-scale Brownian dynamics simulations for semi-dilute solutions with intra- and intermolecular hydrodynamic interactions (HI) and excluded volume (EV), and excellent agreement is obtained using the method of successive fine graining (SFG). In a second project, I will discuss a new method based on passive non-linear microrheology to measure normal stress and extensional viscosity in polymer solutions. Here, we use the Stokes trap combined with particle tracking to study flow-induced particle migration in non-Newtonian solutions. Experimental results are analyzed using a second-order fluid model, which allows for measurement of extensional viscosity. In the final part of the talk, I will discuss our recent work in studying the dynamics of topologically complex polymers such as combs and bottlebrushes using single molecule methods, including relaxation from high stretch, and dynamics in non-equilibrium flow, and single molecule elasticity.
Charles Schroeder is Professor and Ray and Beverly Mentzer Faculty Scholar in the Department of Chemical & Biomolecular Engineering at the University of Illinois at Urbana-Champaign. He is a member of the Center for Biophysics and Computational Biology, with affiliate status in the Department of Materials Science and Engineering, the Department of Chemistry, the Department of Bioengineering, the Frederick Seitz Materials Research Lab, and the Carl Woese Institute for Genomic Biology at Illinois. Professor Schroeder received his B.S. in Chemical Engineering from Carnegie Mellon University in 1999, followed by an M.S. and Ph.D. in Chemical Engineering at Stanford University in 2005 with Eric Shaqfeh and Steve Chu. Before joining the University of Illinois in 2008, he was a postdoctoral fellow at Harvard University and the University of California-Berkeley. Professor Schroeder has been the recipient of several awards, including a Packard Fellowship in Science and Engineering, a Camille Dreyfus Teacher-Scholar Award, an NSF CAREER Award, the Dean’s Award for Excellence in Research, the Arthur B. Metzner Award from the Society of Rheology, and an NIH Pathway to Independence Award (K99/R00).