Squeezing particle-stabilized emulsions into biliquid foams – equation of state

Abstract

Using a centrifuge, we measure the (pressure vs. density) equation of state of Pickering emulsions stabilized by hard-sphere colloids, in order to elucidate the particle contribution to their mechanical properties. Moreover, we have developed a transparent Pickering emulsion, allowing us to determine local volume fraction as a function of distance within the sediment using confocal microscopy, thus extracting an entire equation of state from one centrifugation cycle. We can explain and predict trends in our data using a quantitative model incorporating interdroplet films with a thickness on the scale of the (micron-sized) particles and repulsive interactions across these films. We suggest that the effective repulsion between droplets is due to the deformation of the liquid–liquid interface between particles on one droplet due to compression against a neighbouring droplet.