Dynamic evolution in coarse-grained molecular dynamics simulations of polyethylene melts

Area of Science:

• Computational chemistry
• Polymer physics
• Materials science

Background:

• Coarse-grained (CG) models simplify molecular simulations by representing groups of atoms as single interaction sites.
• Accurate CG models are crucial for simulating large-scale polymer systems beyond the reach of atomistic or united-atom methods.

Purpose of the Study:

• To validate the accuracy of a C50 coarse-grained force field for polyethylene chains of varying lengths (C76 to C300).
• To assess the model's ability to reproduce both static and dynamic properties of polymer chains, including entangled systems.

Main Methods:

• United atom (UA) simulations were used to parameterize the C50 CG model.
• The CG model's performance was evaluated by comparing pair distribution functions, chain dimensions, and diffusion coefficients against UA simulations and experimental data.
• Entanglement length and tube diameter were analyzed using various established methods, including primitive path analysis.

Main Results:

• The C50 CG model accurately reproduced static properties like pair distribution functions and chain dimensions (N^0.5 scaling) for chains up to 300 united atoms.
• Dynamic properties, including diffusion coefficients and entanglement length, were accurately captured.
• The Rouse model's applicability was assessed across different chain lengths (N).

Conclusions:

• The C50 coarse-grained model demonstrates continued accuracy for both static and dynamic properties of polyethylene chains up to C300.
• This validated CG model is suitable for simulating large and entangled polymer systems, offering a computationally efficient approach for molecular dynamics.