Crystal-to-Crystal Transitions in Binary Mixtures of Soft Colloids

TL;DR

This paper presents a reversible method to induce and analyze crystal-to-crystal transitions in binary mixtures of soft colloids, enabling controlled crystallization and phase analysis using microscopy.

Contribution

It introduces a new reversible approach to control and analyze phase transitions in soft colloidal mixtures with in situ salinity tuning.

Findings

Reversible crystal-to-crystal transitions demonstrated in soft colloids.

Enhanced crystallization speed due to particle softness.

Distinct phases identified and characterized via microscopy.

Abstract

In this article, we demonstrate a method for inducing reversible crystal-to-crystal transitions in binary mixtures of soft colloidal particles. Through a controlled decrease of salinity and increasingly dominating electrostatic interactions, a single sample is shown to reversibly organize into entropic crystals, electrostatic attraction-dominated crystals or aggregated gels, which we quantify using microscopy and image analysis. We furthermore analyze crystalline structures with bond order analysis to discern between two crystal phases. We observe the different phases using a sample holder geometry that allows both in situ salinity control and imaging through Confocal Laser Scanning Microscopy, and apply a synthesis method producing particles with high resolvability in microscopy with control over particle size. The particle softness provides for an enhanced crystallization speed, while altering the re-entrant melting behavior as compared to hard sphere systems. This work thus provides several tools for use in the reproducible manufacture and analysis of binary colloidal crystals.