Controlling the Organization of Colloidal Sphero-Cylinders Using Confinement in a Minority Phase.

Niek Hijnen,Paul Clegg

doi:10.3390/gels4010015

Abstract

We demonstrate experimentally that a phase-separating host solvent can be used to organize colloidal rods into different cluster and network states. The rods are silica sphero-cylinders which are preferentially wet by the water-rich phase of an oil–water binary liquid system. By beginning with the rods dispersed in the single-fluid phase and then varying the temperature to enter the demixed regime, a precisely chosen volume of water-rich phase can be created. We then show how this can be used to create independent clusters of rods, a percolating network, a network of clusters or a system that undergoes hindered phase separation. These different modes are selected by choosing the relative volumes of the rods and the water-rich phase and by the timing of the temperature change.

Highlights

Non-spherical colloids move, assemble, and percolate differently compared to standard spherical particles [1,2,3]
We focus here on colloidal sphero-cylinders as model rod-shaped particles; we are interested in their behaviour as they are forced into a confining volume of solvent
Inside the vial [18], the sample changes temperature at a rate of 1 ◦ C/s. This shallow quench leads to liquid–liquid phase separation and the formation of 1 vol % of water-rich phase

Summary

Introduction

Non-spherical colloids move, assemble, and percolate differently compared to standard spherical particles [1,2,3]. Because many natural and synthetic particles, e.g., mineral particles, bacteria, viruses, graphene, carbon nanotubes and fibres are non-spherical, understanding and controlling the new behaviour is valuable [4]. Much has already been achieved by tuning mutual interactions via surface charge or the addition of depletants [5]. Less explored is the approach of organizing non-spherical particles using a phase transition in the host solvent. Low concentrations of rods or platelets can be corralled into a percolating arrangement driven by the phase-separation kinetics. We are considering the host solvent to be a binary mixture of polymers or low molecular weight liquids

Methods

Results

Conclusion