Globule - stretch transitions of collapsed polymers in elongational flow fields

Here we present our studies on the behavior of collapsed polymer chains in elongational flow fields. In particular, we present scaling and hydrodynamic simulation results on the conformation and dynamics of these macromolecules. In the noncollapsed state, we verify via our simulations that there is a smooth transition from a coil to a stretched conformation. The introduction of self-interactions or nonsolvent effects in a polymer, however, suppresses this transition up to a well-defined threshold flow rate ε̇* at which the chain undergoes an immediate and irreversible transition to a stretched conformation. We characterize this behavior under both freely draining and hydrodynamic interacting assumptions and develop scaling arguments to describe the globule-stretch transition in a variety of regimes. The unraveling dynamics and topologies are characterized with relation to these mechanisms, and the elongational viscosity of dilute solutions of collapsed chains is also investigated.