Thermodynamics, Free-Energy Landscapes, and Thermal Transport of Confined Poly(Ethylene Glycol) in CaBTC Metal-Organic Framework.

Nanoscale confinement strongly influences polymer thermodynamics and transport, yet its molecular origins remain unclear. Here, molecular dynamics simulations employing the ReaxFF reactive force field are used to study poly(ethylene glycol) confined within CaBTC metal-organic frameworks at varying pore occupancies. Heat capacities are determined from equilibrium enthalpy, while free-energy landscapes constructed from principal component analysis identify dominant conformational basins and transition barriers. Basin populations and hopping dynamics quantify confinement-induced changes in molecular mobility, and thermal conductivity is evaluated using the Green-Kubo formalism. Confinement stabilizes metastable states, suppresses molecular rearrangements, and leads to systematic, occupancy-dependent variations in thermodynamic and transport behavior.