Looking at the dynamical heterogeneity in a supercooled polymer system through isoconfigurational ensemble

Area of Science:

• Polymer Physics
• Materials Science
• Computational Chemistry

Background:

• Glass formers exhibit slowed and heterogeneous dynamics near the glass transition temperature.
• Dynamic heterogeneity is often linked to increasing spatial correlations and cooperative relaxation regions.

Purpose of the Study:

• To investigate dynamic correlations in polymer systems under supercooling using molecular dynamics.
• To establish the relationship between monomer structure and dynamic behavior via the isoconfigurational ensemble (ICE).

Main Methods:

• Utilized molecular dynamic simulations to study polymer systems in supercooling conditions.
• Employed Pearson's coefficient within the isoconfigurational ensemble (ICE) to analyze dynamic correlations.
• Examined the spatial distribution and temperature dependence of dynamic correlations.

Main Results:

• Dynamic correlations among monomers increase with decreasing temperature and form clusters.
• Regions of high ICE dynamic correlation were found to be spatially distinct from highly mobile or immobile regions.
• Demonstrated a clustering behavior of monomers with the highest correlation, intensifying as temperature drops.

Conclusions:

• The study introduces a novel approach to characterizing dynamic heterogeneity in glass-forming liquids.
• The findings complement traditional mobility-based characterizations by linking dynamic correlations to structural causes.
• The proposed methodology provides an alternative method for observing cooperative relaxation regions.