Helical Packings and Phase Transformations of Soft Spheres in Cylinders

TL;DR

This study investigates how soft microspheres in cylindrical capillaries transition from ordered helical packings to disordered states as their volume fraction decreases, revealing phase transition-like behavior in quasi-one-dimensional systems.

Contribution

It provides experimental evidence of phase transition-like behavior and metastable coexistence in helical packings of soft spheres within cylinders, supported by correlation analysis.

Findings

Ordered packings abruptly become disordered with decreasing volume fraction

Metastable coexistence of ordered and disordered states observed

Correlations and susceptibilities quantify the transition

Abstract

The phase behavior of helical packings of thermoresponsive microspheres inside glass capillaries is studied as a function of volume fraction. Stable packings with long-range orientational order appear to evolve abruptly to disordered states as particle volume fraction is reduced, consistent with recent hard sphere simulations. We quantify this transition using correlations and susceptibilities of the orientational order parameter psi_6. The emergence of coexisting metastable packings, as well as coexisting ordered and disordered states, is also observed. These findings support the notion of phase transition-like behavior in quasi-1D systems.