Composition-Dependent Deformation and Shape-Memory Mechanisms of PETG/POE Blends: An All-Atom Molecular Dynamics Study.

PETG/POE blends are thermo-responsive shape-memory systems with composition-dependent deformation and thermomechanical recovery behavior, but their molecular mechanism remains unclear. In this work, all-atom molecular dynamics simulations were performed for PETG/POE blends with different compositions. Model reliability was supported by density stabilization during equilibration and by reasonable agreement between simulated and experimental glass transition temperatures, with glass transition temperature deviations below 1.3%. Tensile simulations showed that increasing POE content reduced Young's modulus from 1.81 to 1.10 GPa and yield stress from 0.251 to 0.144 GPa, indicating decreased stiffness and enhanced deformation accommodation. Free-volume and cavity analyses indicated tensile-induced packing loosening, cavity nucleation, and subsequent cavity growth and coalescence. Component-resolved interaction-energy decomposition and phase-resolved mean square displacement analyses showed strong PETG-related cohesive interactions, restricted PETG mobility at 200 K, enhanced POE mobility at 450 K, and relatively stronger PETG-POE interactions at intermediate compositions. These results help us to correlate blend composition, local structure, interaction-energy reorganization, chain conformation, and segmental mobility with fixation-recovery behavior. Under the present simulation protocol, PETG4/POE6 showed a relatively balanced response because of the compromise among rigidity, intermolecular interactions, cavity evolution, and thermally activated mobility.