Simple transmission measurements discriminate instability processes in multiple emulsions

Water-in-oil-in-water double emulsions (W1/O/W2) consist of water droplets (W1) dispersed in oil globules (O), which are then redispersed in an external aqueous phase (W2). This paper reports multiple light scattering investigations on W1/O/W2 double emulsions, the inner W1/O emulsion being a concentrated micron sized inverse emulsion, and the outer O/W2 emulsion being a dense direct emulsion. Double emulsions are inherently unstable, and changes of structure can arise from many processes such as instability of both the W1/O and the O/W2 emulsions, and an exchange of water in between the two aqueous phases. Diffuse Transmission Spectroscopy (DTS) is used to follow the structural evolution of these complex systems. We show here that DTS can discriminate between some of the different instability processes of double emulsions. We design three different systems where one of the destabilization processes is dominating, and build different models accounting for the temporal evolution of the turbidity of the system. We find that these models scale well with the experimental data.