Minimal energy packings and collapse of sticky tangent hard-sphere polymers

TL;DR

This study enumerates minimal energy packings of small polymers, explores how collapse dynamics influence structure, and identifies key factors affecting crystallization and disorder in polymer packings.

Contribution

It introduces a systematic enumeration of polymer packings, defines dividing surfaces, and links collapse dynamics to structural and mechanical properties.

Findings

Polymer packings favor intermediate symmetry.

Faster quenches lead to disordered, less crystalline structures.

Crystallization suppression correlates with isostaticity onset.

Abstract

We enumerate all minimal energy packings (MEPs) for small single linear and ring polymers composed of spherical monomers with contact attractions and hard-core repulsions, and compare them to corresponding results for monomer packings. We define and identify ``dividing surfaces" in polymer packings, which reduce the number of arrangements that satisfy hard-sphere and covalent bond constraints. Compared to monomer MEPs, polymer MEPs favor intermediate structural symmetry over high and low symmetries. We also examine the packing-preparation dependence for longer single chains using molecular dynamics simulations. For slow temperature quenches, chains form crystallites with close-packed cores. As quench rate increases, the core size decreases and the exterior becomes more disordered. By examining the contact number, we connect suppression of crystallization to the onset of isostaticity in disordered packings. These studies represent a significant step forward in our ability to predict how the structural and mechanical properties of compact polymers depend on collapse dynamics.