Exploring glass transition in polyethylene via molecular dynamics: From bulk to isolated chain

In this study, we investigate the glass transition behavior of polyethylene (PE) chains in the bulk and isolated, using molecular dynamics (MD) simulations. Leveraging both simulated dilatometry, Arrhenius analysis, and a procedure based on the evolution of percentage of trans states, we identified three distinct regimes with different behaviors, proposing a glass transition domain delimited by glass transition temperatures ( and delimiting the transition domain, and extracted from dilatometry) for bulk polymers. The two latter methods were then used to characterize this domain for isolated chains, allowing us to compare with data stemming from the bulk polymer. Our findings reveal that T g s of an isolated chain are generally lower than that of the bulk except for which remains unchanged. This observation aligns with previous experimental and simulation studies. The study further investigates the dynamic and static flexibilities of the polymer, correlating the potential energy barriers associated with dihedral transitions to the observed and values. We propose that is an intrinsic property of the polymer, as it depends on the potential energy barrier required to escape from the trans state. In contrast, is influenced by more complex interactions and is lower for the isolated chain. • Investigation of Glass Transition in Polyethylene: A comprehensive analysis of glass transition behavior in polyethylene chains, comparing bulk and isolated configurations. • Methodological Advances: Use of molecular dynamics simulations, simulated dilatometry, and a novel method based on trans state evolution to identify glass transition domains. • Correlation of Activation Energies and Transition Temperatures: Demonstrated that the glass transition domain is influenced by potential energy barriers associated with dihedral transitions. • Intrinsic and Environment-Dependent Tg: Identified that the lowest glass transition temperature ( ) is intrinsic to the polymer, while other transition temperatures depend on non-bonding interactions.