Rheology of simple and multiple emulsions

A comprehensive review of the rheology of simple and multiple emulsions is presented. Special attention is given to the models describing the rheology of these systems. The key factors governing the rheology of simple and multiple emulsions are discussed. In general, the state of the art is good for simple emulsions. A priori predictions of the rheological properties of simple emulsions are possible using the existing models. Multiple emulsions have received less attention. Theoretical models describing the rheological behavior of multiple emulsions at arbitrary flow strengths (any shear rate) are lacking. Careful experimental work is needed on the rheology of multiple emulsions of controlled droplet size and morphology. New emerging techniques of producing emulsions, such as microfluidic emulsification, can be used to control and manipulate the number, size, and size distribution of internal droplets in multiple emulsion globules.

Graphical AbstractShear moduli plots (G′ and G′′ versus frequency) and Cole-Cole diagram (η′′ versus η′) for a multiple emulsion composed of type-C globules. Taken from Pal R, On the viscoelastic behavior of multiple emulsions. J. Colloid Interface Sci 2007; 313: 751-6.Figure optionsDownload full-size imageDownload high-quality image (70 K)Download as PowerPoint slideResearch Highlights► Development of viscosity and linear viscoelastic models for concentrated simple and multiple emulsions. ► Influence of additives (surfactants, polymers, solid nanoparticles) on the rheology of emulsions. ► Characterization of electrostatically and sterically stabilized nanoemulsions. ► New technologies for the preparation of simple and multiple emulsions of controlled stability and morphology.