Diffusion in highly concentrated emulsions

High internal phase ratio emulsions (HIPREs) are a kind of emulsions characterized by a dispersed phase volume fraction higher than 0.74. In the last years much attention has been paid to their rheological properties and to their use for the preparation of low-density porous materials. However, in spite of their advantageous features concerning compartmentalization at different scale lengths with hydrophilic and hydrophobic domains and high internal phase ratio, little attention has been given to diffusion, an issue which can have a striking influence in many properties and applications of HIPREs. This review gives an overview on the work carried out in the last years concerning diffusion in highly concentrated emulsions from theoretical and practical points of view.

Graphical abstractRecent work is reviewed concerning diffusion in highly concentrated emulsions as related to the controlled release of actives, the understanding of structural aspects of this kind of emulsions, their colloidal and chemical stability, their use as reactors for synthesis of molecules or materials and the mathematical modelling of the diffusion process.Figure optionsDownload full-size imageDownload high-quality image (88 K)Download as PowerPoint slideHighlights► The solubility of the active and the oil phases determines the release from HIPREs. ► Diffusion is relevant for the chemical and colloidal stability of HIPREs. ► Many diffusion-related issues remain still unexplored, demanding further research.