Can Soft Models Describe Polymer Knots?

Area of Science:

• Polymer Physics
• Computational Materials Science
• Statistical Mechanics

Background:

• Long polymers in melts can form complex knots, analogous to macroscopic ropes.
• Understanding polymer knotting is crucial for predicting material properties.
• Mesoscopic models offer computational efficiency but may oversimplify local polymer interactions.

Purpose of the Study:

• To investigate the validity of mesoscopic polymer models for describing knotting in polymer melts.
• To determine the conditions under which coarse-grained simulations accurately capture polymer topology.
• To compare knotting properties between mesoscopic and microscopic polymer models.

Main Methods:

• Utilized a worm-like chain model for polymer architecture in mesoscopic simulations.
• Employed a generic soft repulsive potential for nonbonded monomer interactions.
• Parametrized the mesoscopic model to match mesoscopic structure and conformations of microscopic reference melts.
• Compared knotting properties across varying chain stiffness in both model types.

Main Results:

• Mesoscopic models accurately predict knotting in stiff polymer melts where stiffness length exceeds excluded volume size.
• Simplified local liquid structure has minimal impact on knotting for stiff chains.
• Mesoscopic models exhibit significant inaccuracies in predicting knotting for flexible polymer melts.

Conclusions:

• Mesoscopic simulations are reliable for studying polymer knots in stiff melts.
• The accuracy of mesoscopic models for polymer topology is dependent on the ratio of chain stiffness to monomer excluded volume.
• Further refinement of mesoscopic models is needed for flexible polymer systems.