Structural transitions and arrest of domain growth in sheared binary immiscible fluids and microemulsions

TL;DR

This study uses lattice Boltzmann simulations to explore how shear and surfactant concentration influence domain growth, arrest, and structural transitions in immiscible fluids and microemulsions, revealing linear dependencies and phase changes.

Contribution

It demonstrates how surfactant concentration controls domain arrest and induces structural transitions under shear in binary and ternary fluid mixtures.

Findings

Surfactant addition arrests domain growth, forming microemulsions.

Maximum domain size and arrest time depend linearly on amphiphile concentration.

Structural transitions from sponge to lamellar phases occur under shear.

Abstract

We investigate spinodal decomposition and structuring effects in binary immiscible and ternary amphiphilic fluid mixtures under shear by means of three dimensional lattice Boltzmann simulations. We show that the growth of individual fluid domains can be arrested by adding surfactant to the system, thus forming a bicontinous microemulsion. We demonstrate that the maximum domain size and the time of arrest depend linearly on the concentration of amphiphile molecules. In addition, we find that for a well defined threshold value of amphiphile concentration, the maximum domain size and time of complete arrest do not change. For systems under constant and oscillatory shear we analyze domain growth rates in directions parallel and perpendicular to the applied shear. We find a structural transition from a sponge to a lamellar phase by applying a constant shear and the occurrence of tubular structures under oscillatory shear. The size of the resulting lamellae and tubes depends strongly on the amphiphile concentration, shear rate and shear frequency.