Local nonequilibrium thermodynamics of polymer collapse dynamics.

Nonequilibrium thermodynamics plays a crucial role in understanding a wide range of physical and chemical processes. While significant advances have been made through frameworks, such as the fluctuation theorem, it remains challenging to define thermodynamic quantities, such as energy, entropy, and free energy, at the local level during nonequilibrium processes. Recently, Jinwoo and Tanaka [Sci. Rep. 5, 7832 (2015)] have proposed a formalism (the JT formalism) that defines local thermodynamic properties via a path ensemble of microstates over time. In this work, we apply the JT formalism to the polymer collapse process as a model nonequilibrium system to observe the collapse dynamics in terms of the end-to-end distance as the mesoscopic variable. Through extensive Langevin dynamics simulations, we quantify conformational free energy, lost information, and nonequilibrium free energy as functions of time and conformation. Our results validate the JT's work fluctuation theorem, which relates work and local nonequilibrium free energy. This study highlights the utility of the JT formalism in analyzing dynamic thermodynamic behavior in complex soft matter systems.