Transferability of a coarse-grained atactic polystyrene model: the non-bonded potential effect

Area of Science:

• Computational chemistry
• Materials science
• Polymer physics

Background:

• Coarse-grained (CG) models simplify complex atomistic systems for efficient simulations.
• Developing accurate CG models requires careful parameterization of inter-particle interactions.
• Atactic polystyrene (PS) is a widely used polymer whose properties are of significant interest.

Purpose of the Study:

• To construct an efficient and simple CG model for atactic polystyrene (PS).
• To derive bonded and non-bonded potentials for the CG force field (FF).
• To investigate the influence of non-bonded potential choice on model accuracy and transferability.

Main Methods:

• A 1:1 mapping scheme was used to create CG beads from atomistic PS.
• Direct Boltzmann inversion and a combined structure-based/thermodynamic method were employed for FF parameterization.
• Lennard-Jones (LJ) potentials were used for non-bonded interactions, parameterized using radial distribution functions (RDF) and bulk density.

Main Results:

• The derived CG model exhibits good temperature transferability from 300 K to 600 K.
• Models with harder LJ potentials show improved density response and temperature transferability.
• The glass transition temperature (Tg) increases with LJ repulsion strength, and thermal expansion coefficients decrease.

Conclusions:

• The CG model with harder LJ potentials provides a more realistic representation of excluded volume interactions.
• This CG model has the potential to accurately predict higher Tg values compared to atomistic systems.
• The chosen FF parameterization method allows for good transferability without temperature-dependent corrections or pressure optimization.