Langevin dynamics simulation of crystallization of ring polymers

Area of Science:

• Polymer science
• Materials science
• Computational chemistry

Background:

• Crystallization in polymers is crucial for material properties.
• Understanding topological effects on polymer crystallization is an ongoing challenge.
• Previous studies have not fully elucidated the distinct crystallization behaviors of ring versus linear polymers.

Purpose of the Study:

• To investigate the fundamental differences in crystallization between single ring polymers and single linear polymers.
• To analyze the early-stage crystallization mechanisms and nucleation processes.
• To explore the impact of topology on secondary nucleation in multi-chain systems.

Main Methods:

• Langevin dynamics simulations were employed.
• A coarse-grained united atom model was utilized.
• Topological effects were isolated to understand crystallization behavior.

Main Results:

• Ring polymers exhibit lower melting temperatures compared to linear polymers, contrary to equilibrium thermodynamics predictions.
• Both ring and linear polymers form 'baby nuclei' during early-stage crystallization, with coarsening dependent on topology.
• Single ring polymers nucleate faster and into metastable lamellar thicknesses than their linear counterparts.
• Secondary nucleation in ring polymers involves free energy barriers, unlike linear polymers.

Conclusions:

• Polymer topology significantly influences crystallization kinetics, nucleation, and melting behavior.
• The findings highlight distinct crystallization pathways for ring and linear polymers, driven by their topological differences.
• Discrepancies with some experimental results suggest that chemical factors, not accounted for in this model, also play a role in polymer crystallization.