Surfactants: Colloid Surfactants for Emulsion Stabilization

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Entry by Grant Gonzalez, 25 Nov 2012

Colloid Surfactants for Emulsion Stabilization

Keywords: Adsorption, Foams, Surfactants

Authors: Jin-Woong Kim, Daeyeon Lee, Ho Cheung Shum, and David A. Weitz

Summary

This paper examines the use of classic solid particles to stabilize emulsions absorbed by wetting as well as the use of Janus particles to drive the adsorption of particles at the monolayer.

Surfactants that accumulate between two immisicible liquids stabilize the separation of the liquid interfaces by forming a monolayer. The monolayer stabilizes the emulsion from coalescence due to its mechanical robustness. However, particle adsorption at the interface is dependent on particle shape, size, wettabilitiy, and inter-particle interaction as the particle needs to be wetted by both liquids. This dependents limits the usefulness of particle stabilization in certain applications.

An alternative strategy to drive surfactants to the liquid-liquid interface is to introduce chemical anisotropy to the stabilizing particles. That is to make the particles themselves amphihilic. Amphihilicity increases liquid-monolayer-liquid interactions due to greater size and greater chemical interaction. Therefore, truly amphiphilic molecules known as Janus particles better stabilize foams.

Furthermore, the surface chemistry of the Janus particles are tunable to increase amphiphilicity and their level of stabilization.

Illustration of the synthesis of an amphiphilic particle dimer and how its properties are tunable.

Janus Particle Control

Within this paper, stabilizing Janus particles are formed via a process that allows for the control of particle geometry and surface chemistry.


An image of the particle stabilzation of oil in water with differing geometries: a) spheres, b) ellipses, c) cylinders.

Discussion

This paper further investigates the driving force behind the adsorption of surfactants at the liquid-liquid interface and explains two types of surfactant stabilization. Furthermore, the paper examines the formation of Janus particles and provides a simple approach to controlling particle geometry and surface chemistry.

Reference

Kin, JW., Lee, Daeyeon, Shun, HC, Weitz, D. A. Colloid Surfactants for Emulsion Stabilization. Advanced Materials. 2008, 3239–3243. 10.1002/adma.200800484.