Morphology and rheology of ternary fluid–fluid–solid systems

Abstract

We examine the effects of interfacially active particles in blends of immiscible homopolymers with a droplet/matrix morphology. The effect of particles on drop size is not monotonic: at low volume fractions (∼0.1%), particles greatly increase the size of the dispersed phase by promoting flow-induced coalescence regardless of which phase wets the particles preferentially. At higher particle loadings (∼1 vol%), the particles completely cover the interface and reduce the size of the dispersed phase. Particles that are preferentially wetted by the continuous phase are also able to glue together two drops by bridging across them. In this case the morphology consists of clusters of particle-bridged drops, and the resulting blends show solid-like rheology. At low particle loadings, most of the particles are sandwiched between drops, leaving the rest of the interface particle-free. At high particle loadings, the entire surface is nearly covered with particles, the drops are faceted, and the morphology resembles a foam structure. In contrast to these results, particles that are preferentially wetted by the dispersed phase or equally wetted by both phases are not capable of bridging, and these blends do not show drop clusters. These results offer new insights on the behavior of ternary systems composed of two fluids and one particulate species.