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Packing structure of semiflexible rings
Leopoldo R Gómez1, Nicolás A García2, Thorsten Pöschel3
1Department of Physics, Universidad Nacional del Sur-IFISUR-CONICET, 8000 Bahía Blanca, Argentina; lgomez@uns.edu.ar.
Summary
Dense polymer ring packing is crucial for understanding biological packaging. X-ray tomography reveals that longer rubber bands form complex, entangled structures within confined spaces, unlike shorter bands.
Area of Science:
- Polymer Physics
- Soft Matter Physics
- Biophysics
Background:
- Understanding the packing of semiflexible rings is essential for polymer dynamics and biological packaging, such as viral circular DNA and genome folding.
- Disordered packings of polymer rings present complex geometrical and topological challenges.
- Semiflexible rings are model systems for various biological and synthetic materials.
Purpose of the Study:
- To investigate the geometrical and topological features of dense, disordered assemblies of semiflexible rings (rubber bands) in a cylindrical container.
- To determine the influence of ring length and confinement on the packing structure.
- To explore the formation of entangled networks within these assemblies.
Main Methods:
- Utilized X-ray tomography to visualize and analyze the 3D structure of packed rubber bands.
- Studied assemblies of varying rubber band lengths under cylindrical confinement.
- Quantified geometrical and topological properties of the band packings.
Main Results:
- Short rubber bands form liquid-like disordered structures with minimal container influence and short-range orientational order.
- Longer rubber bands exhibit folded configurations due to confinement, leading to interpenetration and entanglement.
- A percolating threading network was observed in most systems.
- For very long bands (diameter > 2x container diameter), a complex, fully entangled structure emerged where all bands interpenetrate.
Conclusions:
- The packing structure of semiflexible rings is highly dependent on ring length and degree of confinement.
- Confinement induces significant changes in ring conformation, promoting entanglement and network formation.
- The study provides insights into the fundamental principles governing the packaging of ring-like polymers, relevant to both synthetic materials and biological systems.
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