Crooks Fluctuation Theorem for Single Polymer Dynamics in Time-Dependent Flows: Understanding Viscoelastic Hysteresis

Area of Science:

• Thermodynamics
• Polymer Physics
• Fluid Dynamics

Background:

• Nonequilibrium work relations advance molecular process understanding.
• Fluctuation theorems are key for equilibrium steady-state transitions.
• Limited understanding exists for fluctuation theorems in nonequilibrium steady-states, like polymer stretching in fluid flows.

Purpose of the Study:

• Apply Crooks fluctuation theorem to nonequilibrium thermodynamics of polymer solutions in flow.
• Determine nonequilibrium free energy for single polymer molecules in flow.
• Develop protocols to probe viscoelastic hysteresis and characterize polymer coil-stretch transitions.

Main Methods:

• Utilized single-molecule experiments and Brownian dynamics simulations.
• Developed a time-dependent extensional flow protocol.
• Applied Crooks fluctuation theorem to analyze polymer dynamics.

Main Results:

• Directly determined nonequilibrium free energy for single polymer molecules in flow.
• Characterized viscoelastic hysteresis across various flow strengths.
• Defined quantities to uniquely describe the coil-stretch transition in flowing polymers.

Conclusions:

• Generalized fluctuation theorems offer a robust framework for studying polymer dynamics under far-from-equilibrium conditions.
• This work provides insights into the nonequilibrium thermodynamics of polymer solutions in flow.
• The developed methods enable a deeper understanding of polymer behavior in complex fluid environments.