Temperature-dependent local and global dynamics of atactic polystyrene: A coarse-grained molecular dynamics...

Area of Science:

• Polymer Science
• Computational Chemistry
• Materials Science

Background:

• Coarse-grained (CG) models are essential for simulating polymer dynamics.
• Accurate CG models must preserve structural, thermodynamic, and dynamic properties over wide temperature ranges.
• Developing reliable CG models for atactic polystyrene (PS) is crucial for understanding its behavior.

Purpose of the Study:

• To explore temperature-dependent local and global dynamic properties of atactic PS.
• To assess the dynamic consistency of a structure- and thermodynamics-based CG model with its united-atom (UA) counterpart.
• To compare translational and rotational dynamics across multiple length scales.

Main Methods:

• Systematic coarse-grained (CG) model construction for atactic polystyrene (PS).
• Investigation of translational and rotational dynamics from monomer to global chain scale.
• Comparison of CG and united-atom (UA) models over a broad temperature range.

Main Results:

• The CG model accurately reproduces translational diffusion scaling and relaxation processes observed in the UA model.
• Coupling between conformational relaxation, diffusion, and local structural α-relaxation was identified.
• Both CG and UA models exhibit consistent temperature dependence in diffusion coefficients and relaxation times, following mode-coupling theory predictions.

Conclusions:

• The developed CG model for atactic polystyrene demonstrates high fidelity in reproducing dynamic properties.
• The study validates the CG approach for simulating polymer dynamics and provides a foundation for future model refinement.
• Findings support the use of CG models for quantitative studies of structural relaxation and dynamical heterogeneity near the glass transition temperature.