(171b) Solvent Effects On Hysteresis In the Coil-Stretch Transition

The response of polymer solutions in elongational flow is important for many applications. One key feature of flexible polymers in elongational flow is the sharp transition from a coiled state to stretched state at a critical strain rate. It is important to understand how this transition is altered by polymer-solvent interactions and conformation dependent drag. In theta solvent conditions, conformation dependent drag leads to hysteresis in the transition.

We have recently developed a model of polymer elasticity that includes solvent effects in a new way. Using Brownian Dynamics simulations of this model, we have predicted that some polymers could have dramatically different behavior due to solvent effects; the coil-stretch transition can be eliminated under some conditions. This new model allows us to better understand the importance of molecular flexibility and entropic elasticity in determining the flow response. We will discuss how our model can be used to understand how conformation dependent drag affects the coil-stretch transition in good solvents, comparing a dumbbell model and a bead spring chain model including hydrodynamic interactions between the beads.