(352b) Crooks Fluctuation Theorem for Flowing Complex Fluids

In this work, we apply the Crooks fluctuation theorem to determine fundamental nonequilibrium steady state properties of polymer molecules driven by fluid flow.  In general, nonequilibrium work relations provide a new framework to study the dynamics of complex fluids. Recently, by using the Jarzynski equality, we demonstrated the direct determination of equilibrium properties such as polymer chain elasticity from transient stretching trajectories of polymer molecules in flow. Here, we report the determination of steady state energies of polymers in flow using Brownian dynamics simulations of dsDNA molecules transitioned between strain rates in forward and reverse directions. Interestingly, the steady state energy allows for the determination of rheological quantities such as polymer relaxation time and single chain elasticity. In addition to free energies, we observe a polymer stretch hysteresis in flow that exists in the absence of intra-chain hydrodynamic interactions. We find that the ensemble-average stretching trajectories of polymer molecules strongly depend on the steady state history. Overall, analyzing complex fluids in the context of Crooks fluctuation theorem allows for the determination of fundamental flowing materials properties and the observation of history-dependent phenomena.