Glassy dynamics in two-dimensional ring polymers: size versus stiffness polydispersity.

Area of Science:

• Soft Matter Physics
• Polymer Science
• Materials Science

Background:

• Soft glassy materials are composed of deformable objects.
• Understanding the influence of polydispersity on their dynamics is crucial.

Purpose of the Study:

• Investigate how polydispersity in particle stiffness or size affects the onset of glassy dynamics.
• Model system: two-dimensional assembly of semi-flexible ring polymers.

Main Methods:

• Computational simulations at fixed polydispersity (30%).
• Analysis of ring conformations, orientational order, and bond relaxation pathways.
• Mapping local correlations between ring shape, order, and mobility.

Main Results:

• Stiffness dispersity induces elongated conformations and orientationally ordered structures, causing dynamical slowing.
• Size dispersity creates a bimodal population (small circular, large elongated rings), leading to frustration and delayed arrest.
• Distinct dynamical heterogeneity pathways observed: long-lived domains (stiffness) vs. percolating relaxation (size).

Conclusions:

• The nature of polydispersity (stiffness vs. size) dictates relaxation pathways in soft glasses.
• Stiffness dispersity results in structure-sensitive dynamics.
• Size dispersity activates motion from both circular and elongated populations, influencing emergent glassy dynamics.